Improved structure of rear portion of automotive vehicle body

Abstract: A rear body (1) of an automotive vehicle includes three parts: a front body structural element (2), an intermediate body structural element (3), and a rear body structural element (4) which are castings, joined together. The rigidity of the rear body (1) increases from the rear body structural element (4) to the front body structural element (2), thereby facilitating the ease of collapse of the rear body structural element in response to input of a rear-end collision impact, for the purpose of ensuring a protective structural area at a front side of the rear body.

Description: The present invention relates generally to the structure of a rear portion of a vehicle body for an automotive vehicle. 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 housing 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 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. WO 97/41010 discloses a rear body in accordance with the preamble of claim 1. It would be desirable to be able to improve the structure of a rear portion of an automotive vehicle body in order 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 the invention, there is provided a rear body for an automotive vehicle as set forth in claim 1. The present invention will be understood more fully from the detailed description given hereinbelow and from the accompanying drawings of 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 from the rear of a rear body of an automotive vehicle according to a first embodiment of the invention; Fig. 2 is an exploded perspective view from the front of the rear body; 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 the rear body; Fig. 4 is a perspective view which shows collapse of a rear fender inner in response to input of a collision impact force; Fig. 5 is a lateral sectional view which shows 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 collapse of a rear fender inner when an impact force is applied to one half of a rear end panel; Fig. 7 is a lateral sectional view which shows collapse of a rear fender inner when an impact force is applied to one half of a rear end panel from a diagonal direction; Fig. 8 is a partial sectional view which shows a rear body according to a second embodiment of the invention; Fig. 9 is a partial sectional view which shows a rear body according to a 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. Referring now to the drawings, wherein like numbers refer to like parts in several views, particularly to Figs. 1 to 3, 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 shelf or cross-member 5 and a front portion 6F of each of two rear fender inners 6. The rear body structural element 4 includes a rear portion 6R of each of the rear fender inners 6 and a rear end panel 7. In the following discussion, the front portions 6F and the rear portions 6R 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 6F. Similarly, the rear body structural element 4 has flanges 9 formed on the rear fender inner 6R. 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 6F 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 in-plane pressure exerted on the rear fender inner 6F. 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, but 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 in-plane pressure acting on the front body structural element 2. The ribs 12 also work as stops 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 6R an easy-to-deform portion 21 which serves to facilitate collapse of the rear fender inner 6R 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 6R 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 inners6R. 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 6R 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 6R to the rear end of the rear fender inner 6R. 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 24a in Fig. 3, formed in the ridges 23 of each of the rear fender inners 6R located outward in a widthwise direction of the vehicle body are offset rearward of two of the notches 24, as indicated at 24b, located inward in the widthwise direction of the vehicle body. The rear end panel 7 has an upper half which extends in the widthwise direction of the vehicle body and bulges outward to define a trunk lid receiver 7A and a lower half which bulges inward and has side member mounts 7B formed on ends thereof. The trunk lid receiver 7A 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 25a and vertical ribs 25b provided within a recess formed in an inner wall of the trunk lid receiver 7A. The diagonal ribs 25a extend in a wave form within the trunk lid receiver 7A between the side member mounts 7B. The vertical ribs 25b are arranged outside the diagonal ribs 25a. The trunk lid receiver 7A 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 7A also has an upright bead 27 (which is formed by bulging a central portion of a rear wall thereof inward, serving as a fragile portion). To the inside wall of the side member mounts 7B 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 7B 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 7A 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 as 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 by fixing or replacing the rear body structural element 4 alone. 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 merely 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 6R the easy-to-deform portion 21 serving to facilitate a collapse of the rear fender inner 6R in response to an impact force produced by the rear-end collision of the vehicle. Additionally, the trunk lid receiver 7A 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 6R effectively to induce the collapse of the rear fender inners 6R 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 6R 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 6R 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 6R 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 6R to bulge outward at the notches 24 and the grooves 22 to be opened vertically. The notches 24a which are formed in the ridges 23 defined by the grooves 22a located outward of the vehicle body are, as described above, offset rearward of the notches 24b formed on the ridges 23 defined by the grooves 22b located inward of the vehicle body, thereby causing an outward bulging portion of each of the rear fender inners 6R which is difficult to deform to be collapsed earlier so that the rear fender inners 6R are collapsed in a desired mode. Additionally, the longitudinal offset of the notches 24a and 24b avoids the interference of the vertical deformation of the grooves 22a with that of the grooves 22b, 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 F acts only on one of the rear fender inners 6R 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 6R on the non-collision side. This causes the rear fender inner 6R 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 a 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 comer of the flange 14 to transfer an impact force produced by a rear-end collision of the vehicle into an in-plane pressure acting on the front body structural element 2. Fig. 9 shows the rear body 1 according to a 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 in-plane pressure acting on the intermediate body structural element 3. The ribs 17 also serve as stops 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 6R 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 6R. 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 6R 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 34a, which are formed in the peaks 32a located outward in the widthwise direction of the vehicle body are offset, like the first embodiment, rearward of two of the notches 34, as indicated at 34b, located inward in the widthwise direction of the vehicle body, thereby causing an outmost portion of each of the rear fender inners 6R to be collapsed earlier so that the rear fender inner 6R is collapsed in a desired mode. Additionally, the longitudinal offset of the notches 34a and 34b also serves to avoid the interference of inward bends of the outer peaks 32a at the notches 34a with those of the inner peaks 32b at the notches 34b, 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 6R. 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 from 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. 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.

Claims: A rear body for an automotive vehicle comprising: a front body-structural-element (2) constituting a front portion of the rear body and defining body side inners; a rear body-structural-element (4) constituting a rear portion of the rear body and including rear portions (6R) of rear fender inners (6) and a rear end panel (7); and an intermediate body-structural-element (3) joined to the front and rear body-structural-elements (2,4) and including front portions (6F) of the rear fender inners (6); characterized in that : the front body-structural-element (2) is a casting; the intermediate body-structural-element (3) includes a rear parcel cross-member (5) and is interposed between the front body-structural-element (2) and the rear body-structural-element (4), the intermediate body-structural-element (3) having a rigidity smaller than that of the front body-structural-element (2); and the rear body-structural-element (4) is a casting and has a rigidity smaller than that of the intermediate body-structural-element (3). A rear body as claimed in claim 1, wherein the intermediate body-structural-element (3) has flanges (8) on the front portions (6F) of the rear fender inners (6), the rear body-structural-element (4) has flanges (9) on the rear portions (6R) of the rear fender inners (6), and the intermediate body-structural-element (3) and the rear body-structural-element (4) are joined together by connecting the flanges (8,9) using fastening means (10). A rear body as claimed in claim 1 or 2, wherein the rear body-structural-element (4) has provided in the front portions (6F) of the rear fender inners (6) easy-to-deform portions (21) which serve to facilitate collapse of the front portions (6F) of the rear fender inners (6) in response to input of an impact force produced by a rear-end collision of the vehicle. A rear body as claimed in claim 3, wherein each easy-to-deform portion (21) has a wall of the front portion (6F) of a rear fender inner (6) which bulges outward along a vertical line and is waved to define troughs (22) and ridges (23) extending longitudinally of the rear body, each ridge (23) having in a middle region of its length a fragile portion (24) which serves to induce the front portion (6F) of the rear fender inner to be bent thereat in an inward or outward direction in response to input of an impact force produced by a rear-end collision of the vehicle. A rear body as claimed in claim 4, wherein at least one fragile portion (24a) located outward of the rear body is offset rearward of at least one fragile portion (24b) located inward of the rear body. A rear body as claimed in any of claims 3 to 5, wherein the rear end panel (7) has a load transmitting portion extending in a widthwise direction of the rear body for transmitting an impact force produced by a rear-end collision of the vehicle to the rear fender inners (6). A rear body as claimed in claim 6, wherein the rear end panel (7) has a vertically extending fragile portion (27) formed in a middle region thereof in a widthwise direction of the rear body. A rear body as claimed in claim 1, wherein the rear body-structural-element (4) has an energy absorbing portion for absorbing energy of a collision impact. A rear body as claimed in claim 8, wherein the energy absorbing portion comprises an easy-to-deform portion. A rear body as claimed in claim 9, wherein the easy-to-deform portion comprises a fragile portion (24) between rigid portions (23). A rear body as claimed in claim 9, wherein fragile portions (24,27) are disposed on a rear fender inner and a rear end panel A rear body as claimed in claim 10, wherein the fragile portion comprises a notch (24) and the rigid portion comprises a ridge (23). A rear body as claimed in claim 10, wherein the fragile portion (24) is capable of serving as a pin engage portion when the rear body-structural-element (4) is withdrawn from a mold in a casting process. A rear body as claimed in claim 1, wherein the rigidity is changed by changing wall thickness. A rear body as claimed in claim 2, further comprising ridges (23) connecting with at least one of the flanges (8,9).

Inventors: HANYU ATSUSHI, TOBA RYUICHI, HANYU, ATSUSHI, TOBA, RYUICHI
Applicants: NISSAN MOTOR, NISSAN MOTOR COMPANY, LIMITED
Application year: 2001
Main classification: B62D25
IPC codes: B62D25