Bumper structure for vehicle

Abstract

One embodiment is a bumper structure 10 for a vehicle having a bumper reinforcement 14 and a crush box member 18. A bumper reinforcement end part 14A, which has an open cross-sectional shape, and the crush box member 18, which has an open cross-sectional shape, are joined opposite to each other to form an impact-absorbing part having a cylindrical or substantially closed cross section. The crush box member 18 has at least one deformation starting point part which becomes a starting point of deformation of the impact-absorbing part when the crush box receives an impact load during a collision. The bumper reinforcement end part 14A also deforms according to the deformation of the crush box member 18 starting from the deformation starting point part, whereby the impact load is absorbed by the impact-absorbing part formed by both the crush box member 18 and the bumper reinforcement end part 14A.

Description

Vehicle bumper structure

[0001] The present technology relates to a vehicle bumper structure.

[0002] In some vehicles, crash boxes are provided between both ends of a bumper reinforcement extending in the vehicle width direction and a body frame member. When an impact load is input to the bumper reinforcement due to a collision, the impact load is transmitted to the crash boxes and absorbed by irreversible deformation of the crash boxes.

[0003] A bumper structure such as the one described above is disclosed in, for example, Japanese Patent Application Laid-Open No. 2022-12132. The bumper reinforcement in this bumper structure is a structural member that receives the impact load during a collision, and is not intended to actively deform itself to absorb the impact. The impact load is transmitted from the bumper reinforcement to the crash boxes, which then deform to absorb the impact load. For this reason, the bumper reinforcement itself has a closed cross section over its entire length, which increases the weight of the bumper structure. It is desirable to further increase the amount of energy absorption during a collision and to reduce the weight of the bumper structure.

[0004] One technical aspect disclosed in the present application is a vehicle bumper structure including: a bumper reinforcement extending in a vehicle width direction; and crash box members provided between both end portions of the bumper reinforcement and body frame members; the end portions of the bumper reinforcement have an open cross-sectional shape that is open only on one of the front and rear sides; the crash box members have an open cross-sectional shape that is open only on one of the front and rear sides; the end portions of the bumper reinforcement and the crash box members are joined facing each other to form an impact absorbing portion that is cylindrical or has a substantially closed cross-section; the crash box members have at least one deformation starting point portion that serves as a deformation starting point for the impact absorbing portion when subjected to an impact load during a collision; and as the crash box member deforms starting from the deformation starting point portion, the end portions of the bumper reinforcement also deform, thereby absorbing the impact load by the impact absorbing portion formed by both the crash box member and the end portions of the bumper reinforcement.

[0005] 1 is a schematic diagram of a vehicle body equipped with a bumper according to one embodiment. FIG. 2 is a perspective view of a bumper structure according to one embodiment, viewed from the left rear. FIG. 3 is a cross-sectional view of the bumper structure of FIG. 2 taken along line III-III. FIG. 4 is a cross-sectional view of the bumper structure of FIG. 2 taken along line IV-IV. FIG. 5 is a partially enlarged view showing an attached state in which the bumper structure according to this embodiment is attached via an attachment member on a vehicle body frame member side. FIG. 6 is a cross-sectional view schematically showing deformation behavior when an impact load is input to a vehicle to which the bumper structure according to this embodiment is applied.

[0006] Various embodiments will be described below with reference to the drawings.

[0007] <Automobile Bumper Structure> Fig. 1 schematically shows an automobile bumper structure 10 as one embodiment for receiving a collision load during a collision. The bumper structure 10 is typically disposed at the front and rear of a vehicle body 12 of the automobile along the width direction of the automobile. In Fig. 1, the front of the automobile is indicated by arrow F, and the rear is indicated by arrow R. In the following description, the bumper structure 10 will be described as being disposed at the front of the vehicle body 12. However, as another embodiment, similar features to those described below can also be applied to a bumper structure disposed at the rear of the vehicle body 12.

[0008] As shown in FIGS. 1 and 2 , the bumper structure 10 has a bumper reinforcement 14 and crash box members 18. The bumper reinforcement 14 functions as a core member for providing strength to the bumper structure 10. The bumper reinforcement 14 is disposed along the width direction of the vehicle, and is supported at both ends 14A by the vehicle body frame members 13 (side members extending in the fore-and-aft direction, etc.) via the crash box members 18. In addition, a bumper covering member 16 is disposed so as to cover the outside (front surface) of the bumper reinforcement 14. The bumper covering member 16 is located on the outermost surface of the bumper structure 10, and is designed primarily with the exterior appearance of the vehicle in mind. The bumper covering member 16 is typically formed from a resin suitable for molding designs.

[0009] The crash box members 18 are disposed between the vehicle body frame member 13 and the bumper reinforcement 14 at both end portions 14A of the bumper reinforcement 14 in the longitudinal direction (the width direction as viewed from the vehicle body 12).

[0010] <Bumper Reinforcement> The bumper reinforcement 14 can be formed from a metal plate material. For example, a steel plate material can be used. For example, a high-tensile steel material (tensile strength: 340 MPa to 790 MPa, also referred to as high-tensile steel), an ultra-high-tensile steel material (tensile strength: 980 MPa or more, also referred to as ultra-high-tensile steel), or the like can be used.

[0011] As shown in Figure 3, the bumper reinforcement 14 is formed into a hat-shaped cross section perpendicular to the longitudinal direction. The hat-shaped cross section is formed by press forming into a shape having a side wall portion 20, an upper wall portion 22, a lower wall portion 23, and a flange portion 24. The press forming is performed by bending, drawing, or a combination of these. Therefore, the cross section of the bumper reinforcement 14 is shaped to avoid negative angles that would make it difficult to remove from the mold during press forming.

[0012] As shown in Figure 3, the hat-shaped cross section of the bumper reinforcement 14 has an open shape that is open only in one direction (front-rear and up-down) among four directions (front-rear and up-down). The cross section of the bumper reinforcement 14 has an open shape (hat shape) that is open on the rear side. In the cross-sectional view of Figure 3, the bumper reinforcement 14 has an upper wall portion 22 extending in the front-rear direction, a lower wall portion 23 extending in the front-rear direction, a side wall portion 20 connecting the upper wall portion 22 and the lower wall portion 23 at the front side, and flange portions 24 extending in opposite directions from each end of the upper wall portion 22 and the lower wall portion 23.

[0013] The upper wall portion 22 and the lower wall portion 23 extend rearward from both ends of the side wall portion 20. The upper wall portion 22 and the lower wall portion 23 widen so that the distance between them increases toward the rear. This is an inclined shape that does not form a negative angle that makes demolding difficult. The flange portion 24 of the upper wall portion 22 is formed by extending outward (upward) in the vertical direction from the rear end of the upper wall portion 22. The flange portion 24 of the lower wall portion 23 is formed by extending outward (downward) in the vertical direction from the rear end of the upper wall portion 22.

[0014] 4, the bumper reinforcement 14 also has an upper wall portion 22, a lower wall portion 23, and a side wall portion 20 at both end portions 14A. On the other hand, the end portions 14A of the bumper reinforcement 14 do not necessarily have flange portions 24. However, in another embodiment not shown, the flange portions 24 may extend to the end portions 14A of the bumper reinforcement 14.

[0015] In one embodiment, a normal steel plate with a uniform thickness can be used for the bumper reinforcement 14. Note that, in order to geometrically increase the strength of the side wall portion 20, a recessed bead 26 can be formed in the longitudinal direction at the center position in the width direction of the side wall portion 20. Furthermore, above and below the recessed bead 26, a plurality of recessed beads 27 can be formed intermittently along the longitudinal direction. The end portion 14A of the bumper reinforcement 14 does not have the recessed beads 26, 27.

[0016] <Crash Box> The crash box members 18 can be formed from a metal plate material. For example, a steel plate material can be used. Examples of materials that can be used include high-tensile steel (tensile strength: 340 MPa to 790 MPa, also referred to as high-tensile steel), ultra-high-tensile steel (tensile strength: 980 MPa or more, also referred to as ultra-high-tensile steel), alloyed hot-dip galvanized steel sheet, and hot-dip galvanized steel sheet.

[0017] As shown in Figure 4, the crash box members 18 have an open cross-sectional shape that is open only in one of the four directions (front-rear, front-rear, top-bottom) in a cross-sectional view. The crash box members 18 at the front of the vehicle body 12 have a shape that is open on the front side. The crash box members 18 have an upper surface portion 32, side surfaces 30, and a lower surface portion 33.

[0018] In one embodiment, the crush box member 18 can be a two-piece structure consisting of an upper crush box member 18A and a lower crush box member 18B. In this case, the upper crush box member 18A and the lower crush box member 18B can both have an L-shaped cross section, for example, and can be formed by a well-known progressive die press forming process.

[0019] The upper crash box member 18A has an upper surface portion 32 and an upper side surface portion 30A. The upper surface portion 32 is a surface that extends in the front-to-rear direction. The upper side surface portion 30A extends downward from the rear end of the upper surface portion 32 to form a surface shape. The upper surface portion 32 may be provided with an upper surface bent portion 32X that is bent upward.

[0020] The lower crash box member 18B has a lower surface portion 33 and a lower side surface portion 30B. The lower surface portion 33 is a surface that extends in the front-to-rear direction. The lower side surface portion 30B extends upward from the rear end of the lower surface portion 33 to form a surface shape. The lower surface portion 33 may be provided with a lower surface bent portion 33X that is bent downward.

[0021] The side surface portion 30 is composed of both an upper side surface portion 30A and a lower side surface portion 30B. That is, the side surface portion 30 has a surface shape formed by the upper side surface portion 30A extending from the rear end of the upper surface portion 32 and the lower side surface portion 30B extending from the rear end of the lower surface portion 33. In other words, the crash box member 18 has a structure in which the side surface portion 30 is divided into the upper side surface portion 30A and the lower side surface portion 30B at the middle portion thereof.

[0022] 2, the upper crash box member 18A and the lower crash box member 18B are joined together by spot welding, and the figure shows some spot welding points S.

[0023] In an alternative embodiment (not shown), the crush box member 18 may be a one-piece member having a C-shaped cross section instead of the two-piece structure described above.

[0024] <Impact Absorbing Portion> As shown in Figure 4, an impact absorbing portion having a cylindrical shape or a substantially closed cross section is formed by joining the openings of the end portion 14A of the bumper reinforcement 14 and the crush box member 18 so that they face each other. The outer surfaces of the upper surface portion 32 and the lower surface portion 33 of the crush box member 18 are joined in surface contact with the inner surface of the end portion 14A of the bumper reinforcement 14. Specifically, the outer surface (upper surface) of the upper surface portion 32 of the crush box member 18 is joined by spot welding in surface contact with the inner surface (lower surface) of the upper wall portion 22 of the end portion 14A of the bumper reinforcement 14. The outer surface (lower surface) of the lower surface portion 33 of the crush box member 18 is joined by spot welding in surface contact with the inner surface (upper surface) of the lower wall portion 23 of the end portion 14A of the bumper reinforcement 14.

[0025] 2 and 5, the crash box member 18 has an overall box-like shape. The outer surface of the crash box member 18 has a ridge 19 (a boundary between surfaces) extending toward the body frame member 13. The crash box member 18 and the end 14A of the bumper reinforcement 14 are spot-welded at a position on the ridge 19 or a position adjacent to the ridge 19 (spot welding point S). By positioning the spot welding point S near the ridge 19 of the crash box member 18, which is a highly rigid portion, the load P is more easily transmitted from the end 14A of the bumper reinforcement 14 to the crash box member 18, which receives the impact load. This improves the efficiency of impact load transmission between the components and increases the amount of energy absorption.

[0026] The portion of the bumper reinforcement 14 other than the end 14A may have an open cross section. However, in another embodiment not shown, the portion of the bumper reinforcement 14 other than the end 14A may have a closed cross section by closing the open side (rear side) with a closing member. However, it is preferable that such a closing member is not continuous with the crash box members 18 so as not to interfere with the independent deformation of the crash box members 18 for impact absorption.

[0027] <Mounting Member> As shown in Figure 5, mounting members 40 can be arranged between the crash box members 18 and the vehicle body frame member 13 to mount the assembly (bumper structure 10) consisting of the bumper reinforcement 14 and the crash box members 18 to the vehicle body frame member 13. The ridge lines 19 of the crash box members 18 are arranged to face the ridge lines 42 of the mounting members 40. By aligning the ridge lines 19 of the crash box members 18 and the ridge lines 42 of the mounting members 40, the efficiency of the transmission of the impact load P between the components can be improved, and the amount of energy absorption can be increased. Note that the mounting members 40 themselves can be designed without assuming impact absorption.

[0028] <Deformation Behavior of Bumper Structure During Collision> Using Figure 6, the deformation behavior when an impact load P is input to a vehicle to which the bumper structure according to the above-described embodiment is applied will be described. The impact load P acting on the center portion of the bumper structure 10 due to a frontal collision of the vehicle is first received by the bumper reinforcement 14. The load acting on the bumper reinforcement 14 is then transmitted to the vehicle body 12 via the crash box members 18 disposed at both ends of the bumper reinforcement 14. At this time, the impact absorbing portions formed by the end portions 14A of the bumper reinforcement 14 and the crash box members 18 undergo irreversible deformation and absorb at least a portion of the collision energy. In other words, the end portions 14A of the bumper reinforcement 14, together with the crash box members 18, form components of the crash boxes.

[0029] Specifically, the crash box member 18 has upper surface bent portions 32X and lower surface bent portions 33X, which serve as deformation origins (deformation-inducing portions) of the impact absorbing portion when subjected to an impact load P during a frontal collision. The upper surface bent portions 32X bend further upward as the impact load P is input. The lower surface bent portions 33X bend further downward as the impact load P is input. The upper surface bent portions 32X and the lower surface bent portions 33X bulge outward as the impact load P is input, causing the crash box member 18 to undergo irreversible deformation associated with absorbing the impact load P. At this time, as the upper surface bent portions 32X and the lower surface bent portions 33X (deformation origin portions) of the crash box member 18 deform, the upper wall portion 22 and the lower wall portion 23 of the end portion 14A of the bumper reinforcement 14 deform so as to expand outward. That is, the impact load P is absorbed by the crash boxes formed by both the crash box members 18 and the ends 14A of the bumper reinforcement 14. In this way, the range in which the bumper structure 10 of this embodiment can absorb collision energy extends not only to the crash box members 18 but also to the ends 14A of the bumper reinforcement 14, thereby improving the amount of energy absorption.

[0030] The required performance of the bumper structure 10 of this embodiment was verified in terms of the three-point bending strength and energy absorption performance. As a result, the three-point bending strength met the required performance. Furthermore, when the center pendulum test, corner pendulum test, and damage test were carried out for the energy absorption performance, the required performance was also met for both the energy absorption amount and the maximum load.

[0031] <Effects of the above embodiment> Finally, advantageous effects of the above embodiment will be noted.

[0032] The bumper structure 10 includes a bumper reinforcement 14 extending in the vehicle width direction and crash box members 18 provided between both end portions of the bumper reinforcement 14 and a body frame member 13. The end portion 14A of the bumper reinforcement 14 has an open cross-sectional shape that is open only on one of the front and rear sides, and the crash box member 18 has an open cross-sectional shape that is open only on one of the front and rear sides. The end portion 14A of the bumper reinforcement 14 and the crash box member 18 are joined facing each other to form an impact absorbing portion having a cylindrical or substantially closed cross-section. The crash box member 18 has at least one deformation starting point portion that serves as a starting point for deformation of the impact absorbing portion when subjected to an impact load P during a collision. In the bumper structure 10, the end portion 14A of the bumper reinforcement 14 also deforms in conjunction with deformation of the crash box member 18 starting from deformation of the deformation starting point portion, and thus the impact load P is absorbed by the impact absorbing portion formed by both the crash box member 18 and the end portion 14A of the bumper reinforcement 14. As a result, the range that absorbs the impact load P extends not only to the crash box member 18 but also to the end 14A of the bumper reinforcement 14 (the end 14A of the bumper reinforcement 14 is also a component of the crash box), thereby improving the amount of energy absorption. In addition, because at least the end 14A of the bumper reinforcement 14 has an open cross-sectional shape, the weight of the bumper structure 10 is reduced.

[0033] In some embodiments, the crash box member 18 has an upper surface portion 32 extending in the front-rear direction, a lower surface portion 33 extending in the front-rear direction, and side surface portions 30 extending from the ends of the upper surface portion 32 and the lower surface portion 33 to form a surface shape. The upper surface portion 32 has upper surface bent portions 32X whose plate surfaces are bent to function as deformation origin portions, and the lower surface portion 33 has lower surface bent portions 33X whose plate surfaces are bent to function as deformation origin portions. In the crash box member 18, the upper surface bent portions 32X and the lower surface bent portions 33X deform outward and away from each other upon input of an impact load P. The deformation origin portions are formed by the upper surface bent portions 32X of the upper surface portion 32 and the lower surface bent portions 33X of the lower surface portion 33, which are bent plate surfaces. This allows for control of deformation behavior with a simple configuration without adopting a complex configuration or increasing the number of parts.

[0034] In some embodiments, the crush box member 18 is joined with the outer surface of the upper surface portion 32 and the outer surface of the lower surface portion 33 in surface contact with the inner surface of the end portion 14A of the bumper reinforcement 14. The crush box member 18 exhibits a deformation behavior in which the upper surface portion 32 and the lower surface portion 33 spread (push) the upper wall portion 22 and the lower wall portion 23 of the end portion 14A of the bumper reinforcement 14 outward, making it easy to deform.

[0035] In some embodiments, the crush box member 18 is divided into an upper crush box member 18A and a lower crush box member 18B at the middle portion of the side portion 30. This makes it easy to apply to a progressive die.

[0036] In some embodiments, the outer surface of the crash box member 18 has a ridge line 19 extending toward the body frame member 13, and the crash box member 18 and the end 14A of the bumper reinforcement 14 are spot welded to each other at a position on or adjacent to the ridge line 19. By setting the spot weld points S near the ridge line 19 of the crash box member 18, which is a highly rigid portion, the load P is more easily transmitted from the end 14A of the bumper reinforcement 14 that has received the impact load P to the crash box member 18, improving the efficiency of the transmission of the impact load P between the parts and increasing the amount of energy absorption.

[0037] In some embodiments, mounting members 40 for mounting the crash box members 18 are disposed between the crash box members 18 and the body frame member 13, and the ridge lines 19 of the crash box members 18 are arranged so as to face the ridge lines 42 of the mounting members 40. By aligning the ridge lines 19 of the crash box members 18 with the ridge lines 42 of the mounting members 40, the efficiency of the transmission of the impact load P between the components can be improved, and the amount of energy absorption can be increased.

[0038] Although various embodiments have been described above, the technology disclosed herein is not limited to these embodiments, and those skilled in the art can make various modifications, additions, and omissions.

Claims

1. A vehicle bumper structure comprising: a bumper reinforcement extending in a vehicle width direction; and crash box members provided between both ends of the bumper reinforcement and a vehicle body frame member, wherein the ends of the bumper reinforcement have an open cross-sectional shape that is open only on one of the front and rear sides, and the crash box members have an open cross-sectional shape that is open only on one of the rear and front sides, and an impact absorbing section having a cylindrical or substantially closed cross section is formed by joining the ends of the bumper reinforcement and the crash box members facing each other, and the crash box members have at least one deformation starting point portion that becomes a starting point for deformation of the impact absorbing section when an impact load is received during a collision, and the ends of the bumper reinforcement also deform together with deformation of the crash box member starting from the deformation starting point portion, thereby absorbing the impact load by the impact absorbing section formed by both the crash box member and the ends of the bumper reinforcement.

2. A vehicle bumper structure as described in claim 1, wherein the crash box member has an upper surface portion extending in the fore-and-aft direction of the vehicle, a lower surface portion extending in the fore-and-aft direction of the vehicle, and side portions extending from the ends of the upper surface portion and the ends of the lower surface portion to form a surface shape, the upper surface portion has an upper surface bent portion that functions as the deformation starting point portion, and the lower surface portion has a lower surface bent portion that functions as the deformation starting point portion, and the crash box member has a vehicle bumper structure in which the upper surface bent portion and the lower surface bent portion deform so as to move away from each other outward as the impact load is input.

3. A vehicle bumper structure as described in claim 2, wherein the outer surface of the upper portion and the outer surface of the lower portion of the crash box member are joined in surface contact with the inner surface of the end portion of the bumper reinforcement.

4. A vehicle bumper structure as claimed in claim 2 or 3, wherein the crash box member is divided into an upper crash box member and a lower crash box member at a middle portion of the side portion.

5. A vehicle bumper structure as claimed in claim 4, wherein the outer surface of the crash box member has a ridge line extending towards the vehicle body frame member, and the ends of the crash box member and the bumper reinforcement are spot welded to a position on the ridge line or a position adjacent to the ridge line.

6. A vehicle bumper structure as claimed in claim 4, wherein the crash box members are configured to be attached via mounting members provided on the vehicle body frame member side, and the ridges of the crash box members are arranged to face the ridges of the mounting members.

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