Structure of rear portion of automotive vehicle body

1 Technical Field

The present invention relates generally to an improved structure of a rear portion of an automotive vehicle body.

2 Background Art

Japanese Patent First Publication No. 10-129533 shows a rear body of a vehicle in which a reinforcement member is installed diagonally to connect an end portion of each rear side member to an end portion of a rear cross member across a joint of them to increase the torsional rigidity of the rear portion of the vehicle body, thereby distributing the energy of an impact force upon occurrence of a rear-end collision of the vehicle to the rear side members, the rear cross member, and rear wheel houses so as to define an impact absorbing structural portion occupying a portion of the vehicle body in front of the reinforcement members and a vehicle body deformable portion occupying the remaining portion of the vehicle body on the rear side of the reinforcement members.

Specifically, the above vehicle body structure is designed to absorb the energy of an impact force produced by a rear-end collision of the vehicle through structural members such as the rear side members arranged at a lower portion of the vehicle body and thus encounters the drawback in that it is very difficult to distribute the energy of the impact force up to an upper portion of the vehicle body effectively. Further, since the lower portion of the vehicle body absorbs the energy of the impact force as a whole, the need may arise for reconditioning or replacing the whole rear portion of the vehicle body.

It is an object of the present invention to provide an improved structure of a rear portion of an automotive vehicle body which is designed to absorb the energy of impact produced by a vehicle collision through both an upper and a lower portion of the vehicle body.

According to one aspect of the invention, there is provided a rear body of an automotive vehicle which comprises: a front body structural element made of a cast defining a front portion of the rear body; and a rear body structural element made of a cast. The rear body structural element is joined to said front body structural element to define a rear portion of the rear body and has a rigidity smaller than that of the front body structural element.

The present invention will be understood more fully from the detailed description given hereinbelow and from the accompanying drawings of the preferred embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments but are for the purpose of explanation and understanding only.

In the drawings:

FIG. 1 is an exploded perspective view which shows a rear body of an automotive vehicle according to the first embodiment of the invention;

FIG. 2 is an exploded perspective view which shows a rear body according to the first embodiment of the invention;

FIG. 3 is a lateral sectional view which shows a front body structural element, an intermediate body structural element, and a rear body structural element of a rear body;

FIG. 4 is a perspective view which shows a collapse of a rear fender inner in response to input of a collision impact force;

FIG. 5 is a lateral sectional view which shows a collapse of rear fender inners when a vehicle is involved in a full lap rear-end collision;

FIG. 6 is a lateral sectional view which shows a collapse of a rear fender inner when an impact force is applied to a half of a rear end panel;

FIG. 7 is a lateral sectional view which shows a collapse of a rear fender inner when an impact force is applied to a half of a rear end panel from a diagonal direction;

FIG. 8 is a partial sectional view which shows a rear body according to the second embodiment of the invention;

FIG. 9 is a partial sectional view which shows a rear body according to the third embodiment of the invention; and

FIGS. 10 and 11 are partial perspective views which show a modified form of an easy-to-deform portion of each rear fender inner of a rear body structural element 4 .

Referring now to the drawings, wherein like numbers refer to like parts in several views, particularly to FIGS. 1, there is shown an improved structure of a rear portion of an automotive vehicle body according to the invention

A rear body 1 is made of a lightweight metallic material such as aluminum alloy and has three parts: a front body structural element 2 , an intermediate body structural element 3 , and a rear body structural element 4 which are arrayed longitudinally of a vehicle body. The front body structural element 2 forms body side inners. The intermediate body structural element 3 includes a rear parcel 5 and a front portion 6 F of each rear fender inner 6 . The rear body structural element 4 includes a rear portion 6 R of each of the rear fender inners 6 and a rear end panel 7 . In the following discussion, the front portions 6 F and the rear portions 6 R of the rear fender inners 6 will be referred to as a rear fender inner of the intermediate body structural element 3 and a rear fender inner of the rear body structural element 4 , respectively.

The rear body structural element 4 is lower in rigidity than the intermediate body structural element 3 . The rear body structural element 4 is smaller in lateral cross section than the intermediate body structural element 3 . The rear body structural element 3 decreases gradually in lateral cross section toward the rear end panel 7 . The wall thickness of the rear body 1 increases from the rear body structural element 4 to the intermediate body structural element 3 and to the front body structural element 2 , thereby increasing the rigidity of the rear body 1 gradually from the rear body structural element 4 to the front body structural element 2 .

The intermediate body structural element 3 has flanges 8 formed on the rear fender inners 6 F. Similarly, the rear body structural element 4 has flanges 9 formed on the rear fender inner 6 R. The intermediate body structural element 3 and the rear body structural element 4 are joined to each other, as clearly shown in FIG. 3, by connecting the flanges 8 and 9 together through fastening members 10 such as rivets.

The rear body structural element 4 is, as discussed above, smaller in lateral cross section thereof than the intermediate body structural element 3 . The flange 9 of the rear body structural element 4 is bent outward, while the flange 8 of the intermediate body structural element 3 is bent inward so that the flanges 8 and 9 may be brought into surface-to-surface contact.

The intermediate body structural element 3 has ribs 11 formed on an inner wall of each of the rear fender inners 6 F in contact with the flange 8 for transferring the impact acting on the rear body structural element 4 upon occurrence of a rear-end collision of the vehicle into an inplane pressure exerted on the rear fender inner 6 F.

The intermediate body structural element 3 is, as clearly shown in FIG. 3, lapped partially in the front body structural element 2 and welded as indicated at W.

The intermediate body structural element 3 is, as described above, smaller in wall thickness than the front body structural element 2 as a whole, however, it has a thick end portion welded to the front body structural element 2 whose thickness is substantially equal to that of the front body structural element 2 for increasing the strength of connection between the intermediate body structural element 3 and the front body structural element 2 .

The front body structural element 2 has a plurality of ribs 12 formed integrally on an inner wall thereof which are in contact with the end of the intermediate body structural element 3 when the front body structural element 2 and the intermediate body structural element 3 are joined together, thereby transferring the collision impact transmitted from the intermediate body structural element 3 into an inplane pressure acting on the front body structural element 2 . The ribs 12 also work as stoppers which assist in positioning the front body structural element 2 longitudinally when joined to the intermediate body structural element 3 .

The rear body structural element 4 has formed in each of the rear fender inners 6 R an easy-to-deform portion 21 which serves to facilitate a collapse of the rear fender inner 6 R in response to input of the impact produced by the rear-end collision of the vehicle.

Each of the easy-to-deform portions 21 has V-shaped grooves 22 formed at given vertical intervals in an outer wall of one of the rear fender inner 6 R bulging outward along a vertical car line. The grooves 22 extend longitudinally of the vehicle body and define ridges 23 on an inner wall of each of the rear fender inners 6 R. Each of the ridges 23 has a notch 24 formed in the longitudinal center thereof which serves to induce a corresponding one of the rear fender inners 6 R to be collapsed easily so that the grooves 22 may be opened vertically when the vehicle is involved in a rear-end collision.

The grooves 22 extend from the flange 9 of each of the rear fender inners 6 R to the rear end of the rear fender inner 6 R. Each of the notches 24 also serves as a step with which an end of an ejector pin (not shown) engages when the rear body structural element 4 is withdrawn (in a longitudinal direction of the vehicle body in the drawing) from a mold in a casting process.

Two of the notches 24 which are, as indicated at 24 a in FIG. 3, formed in the ridges 23 of each of the rear fender inners 6 R located outward in a width-wise direction of the vehicle body are offset rearward of two of the notches 24 , as indicated at 24 b, located inward in the width-wise direction of the vehicle body.

The rear end panel 7 has an upper half which extends in the width-wise direction of the vehicle body and bulges outward to define a trunk lid receiver 7 A and a lower half which bulges inward and has side member mounts 7 B formed on ends thereof.

The trunk lid receiver 7 A has, as clearly shown in FIG. 2, a load transmitting means 25 formed over a length thereof which works to transmit a rear-end collision impact force to the rear fender inners 6 . The load transmitting means 25 is made up of diagonal ribs 25 a and vertical ribs 25 b provided within a recess formed in an inner wall of the trunk lid receiver 7 A. The diagonal ribs 25 a extend in a wave form within the trunk lid receiver 7 A between the side member mounts 7 B. The vertical ribs 25 b are arranged outside the diagonal ribs 25 a.

The trunk lid receiver 7 A has formed in a central portion of an upper surface thereof a striker receiver 26 into which a striker of a lock mechanism of a trunk (not shown) is fitted. The trunk lid receiver 7 A also has a upright bead 27 which is formed by bulging a central portion of a rear wall thereof inward as serving as a fragile portion.

To the inside wall of the side member mounts 7 B of the rear body structural element 4 , side members (not shown) are joined, while to the outside wall thereof, member extensions (not shown) are joined in alignment with the side members. Each of the side member mounts 7 B has, as shown in FIG. 1, a vertical rib 28 which is formed on the outside wall thereof and extends up to an outer bottom wall of the trunk lid receiver 7 A for increasing the rigidity thereof.

As described above, the rear body 1 is made up of three cast parts: the front body structural element 2 , the intermediate body structural element 3 , and the rear body structural element 4 which are arrayed longitudinally of the vehicle body. The wall thickness of the rear body 1 increases from the rear body structural element 4 to the intermediate body structural element 3 and to the front body structural element 2 , and the rear body structural element 4 decreases in lateral cross section gradually, thereby increasing the rigidity of the rear body 1 from the rear body structural element 4 to the front body structural element 2 . This induces the rear body 1 to be collapsed in the order of the rear body structural element 4 , the intermediate body structural element 3 , and the front body structural element 2 when the vehicle is involved in a rear-end collision of the vehicle. Specifically, the rear body 1 absorbs the energy of collision impact as a whole a s well as the absorption by lower portions of the rear side members.

The rigidity of the rear body 1 , as described above, increases from the rear body structural element 4 to the intermediate body structural element 3 and to the front body structural element 2 , that is, as approaching the vehicle cabin. Specifically, the rear body 1 is so designed as to have the greatest resistance to the collapse caused by a rear-end collision in the front body structural element 2 and induce the rear body structural element 4 to be collapsed easily, thereby minimizing the amount of collapse of the front body structural element 2 and the intermediate body structural element 3 to provide a protective structural area as great as possible to the front of the rear body 1 close to the vehicle cabin.

In the event of a light rear-end collision, only the rear body structural element 4 is collapsed, which allows the rear body 1 to be reconditioned only by fixing or replacing the rear body structural element 4 . Particularly, the rear body structural element 4 and the intermediate body structural element 3 are joined by connecting the flanges 9 and 8 using the fastening members 10 , thus allowing the rear body structural element 4 to be replaced easily only by removing the fastening member 10 from the flanges 8 and 9 .

Further, the joining of the rear body structural element 4 and the intermediate body structural element 3 using the flanges 9 and 8 increases the degree of transmission of the rear-end collision impact force from the rear body structural element 4 to the front body structural element 2 through the intermediate body structural element 3 and also ensures a higher resistance of the rear body structural element 4 to the collapse.

The rear body structural element 4 , as described above, has formed in each of the rear fender inners 6 R the easy-to-deform portion 21 serving to facilitate a collapse of the rear fender inner 6 R in response to an impact force produced by the rear-end collision of the vehicle. Additionally, the trunk lid receiver 7 A of the rear end panel 7 has the load transmitting means 25 which works to transmit the rear-end collision impact force to the rear fender inners 6 . The rear-end collision impact force is, thus, transmitted to the right and left rear fender inners 6 R effectively to induce the collapse of the rear fender inners 6 R from the easy-to-deform portions 21 , thereby resulting in collapse of the rear body structural element 4 in an optimum deformation mode.

Each of the easy-to-deform portions 21 has the V-shaped grooves 22 extending in parallel at a given vertical interval and the notches 24 formed in the central portions of the ridges 23 defined by the grooves 22 so that the rear fender inners 6 R may be bent inward at the notches 24 upon input of the rear-end collision impact force, causing the grooves 23 to be opened vertically. Specifically, the collapse of each of the rear fender inners 6 R includes, as shown in FIG. 4, the vertical deformation of the grooves 22 and an outward bulge thereof, thereby absorbing the energy of the rear-end collision impact effectively.

For example, when the vehicle is involved in the so-called full lap collision in which an impact force F, as shown in FIG. 5, acts on the rear end panel 7 from a perpendicular direction, the impact force F is distributed equally to the right and left rear fender inners 6 R through the load transmitting means 25 , so that the stress concentrates at the notches 24 formed in the ridges 23 of the easy-to-deform portions 21 , thereby causing the rear fender inners 6 R to bulge outward at the notches 24 and the grooves 22 to be opened vertically.

The notches 24 a which are formed in the ridges 23 defined by the grooves 22 a located outward of the vehicle body are, as described above, offset rearward of the notches 24 b formed on the ridges 23 defined by the grooves 22 b located inward of the vehicle body, thereby causing an outward bulging portion of each of the rear fender inners 6 R which is difficult to deform to be collapsed earlier so that the rear fender inners 6 R are collapsed in a desired mode.

Additionally, the longitudinal offset of the notches 24 a and 24 b avoids the interference of the vertical deformation of the grooves 22 a with that of the grooves 22 b, thereby enhancing the efficiency in absorbing the energy of collision impact.

FIG. 6 shows a collapse of the rear end panel 7 when the vehicle is involved in the so-called offset rear-end collision in which the impact force F is applied to a half of the rear end panel 7 from a perpendicular direction. In this case, the impact force Facts only on one of the rear fender inners 6 R located on the collision side, but the bead 27 extending vertically in the central portion of the rear end panel 7 works as a fragile portion to induce the rear end panel 7 to be bent at the center thereof, so that the impact force F is transmitted as the moment of force to the other rear fender inner 6 R on the non-collision side. This causes the rear fender inner 6 R on the non-collision side to be collapsed through the easy-to-deform portion 21 , thereby absorbing the impact force F completely. Substantially the same collapse of the rear end panel 7 is also taken place when the impact force F acts, as shown in FIG. 7, on the rear end panel 7 from a diagonal direction.

FIG. 8 shows the rear body 1 according to the second embodiment of the invention which is different from the first embodiment in a connection of the front body structural element 2 and the intermediate body structural element 3 . Other arrangement are identical, and explanation thereof in detail will be omitted here.

The front body structural element 2 has a flange 14 bent inward. The intermediate body structural element 3 has a flange 15 bent outward. The front body structural element 2 and the intermediate body structural element 3 are jointed by welding the flange 15 on the flange 14 , as indicated at W. A plurality of ribs 16 are formed on an inner corner of the flange 14 to transfer an impact force produced by a rear-end collision of the vehicle into an inplane pressure acting on the front body structural element 2 .

FIG. 9 shows the rear body 1 according to the third embodiment of the invention which is different from the first embodiment in a connection of the intermediate body structural element 3 and the rear body structural element 4 . Other arrangement are identical, and explanation thereof in detail will be omitted here.

The rear body structural element 4 is lapped at an end portion thereof over the intermediate body structural element 3 and joined together by fastening members 10 such as rivets.

A plurality of ribs 17 are formed integrally on an inner wall of the intermediate body structural element 3 which are in contact with an end of the rear body structural element 4 when the intermediate body structural element 3 is joined to the rear body structural element 4 for transferring a rear-end collision impact force exerted on the rear body structural element 4 into an inplane pressure acting on the intermediate body structural element 3 . The ribs 17 also serve as stoppers for positioning the rear body structural element 4 when fitted into the intermediate body structural element 3 .

FIGS. 10 and 11 show a modification of the easy-to-deform portion 21 of each of the rear fender inners 6 R of the rear body structural element 4 .

The easy-to-deform portion 21 is made of a wall which is corrugated to define V-shaped troughs 22 and peaks 32 extending horizontally and which bulges, like the first embodiment, outward as a whole along a vertical car line of the rear fender inner 6 R. The V-shaped troughs 22 have substantially the same length as that of the grooves 22 in the first embodiment. Each of the peaks 32 has a notch 34 formed in a central portion of the ridge 33 for inducing the rear fender inner 6 R to be collapsed easily at the notches 34 when a rear-end collision impact force F, as shown in FIG. 11, is applied to the rear end panel 7 .

Two of the notches 34 , as indicated at 34 a, which are formed in the peaks 32 a located outward in the width-wise direction of the vehicle body are offset, like the first embodiment, rearward of two of the notches 34 , as indicated at 34 b, located inward in the width-wise direction of the vehicle body, thereby causing an outmost portion of each of the rear fender inners 6 R to be collapsed earlier so that the rear fender inner 6 R is collapsed in a desired mode.

Additionally, the longitudinal offset of the notches 34 a and 34 b also serves to avoid the interference of inward bends of the outer peaks 32 a at the notches 34 a with those of the inner peaks 32 b at the notches 34 b, thereby enhancing the efficiency in absorbing the energy of collision impact.

Notches, like the first embodiment, may also be formed in the inner wall (i.e., the troughs 22 ) of the rear fender inners 6 R.

As apparent from the above discussion, the structure of the rear body 1 is so designed as to facilitate the ease of collapse of a rear portion thereof (i.e., the rear body structural element 4 ) for absorbing the energy of a collision impact force acting on the rear of the vehicle body in an ideal mode to provide an occupant protective area on the front side of the rear body 1 . Further, the rear body 1 is fabricated by three cast parts: the front body structural element 2 , the intermediate body structural element 3 , and the rear body structural element 4 , thus decreasing the number of parts and production processes greatly as compared with a conventional structure of a rear body made by assembling many panel members. The assembly of the vehicle body may be accomplished by preparing a subassembly made up of the body structural elements 2 , 3 , and 4 and then joining it to a front body, thereby facilitating the ease of automatic assembly of the vehicle body and resulting in a decrease in manufacturing cost.

The rear body 1 may alternatively be made up of two separate cast parts: one being an one-piece structural member including the front body structural element 2 and the intermediate body structural element 2 integrally and the other being the rear body structural element 4 .

The entire contents of Japanese Patent Application No. 2000-66534 (filed on Mar. 10, 2000) is incorporated herein by reference.

While the present invention has been disclosed in terms of the preferred embodiments in order to facilitate better understanding thereof, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention. Therefore, the invention should be understood to include all possible embodiments and modifications to the shown embodiments which can be embodied without departing from the principle of the invention as set forth in the appended claims.