JP5235007B2 - Crash box - Google Patents

Description

  The present invention relates to a crash box (energy absorbing member) that is deformed by receiving a collision load in the axial direction and absorbs collision energy when a car body collides.

  Inside the bumper attached to the front end (front) and rear end (rear) of a car body such as an automobile, it extends over the width of the car body. Bumper reinforcements are provided that crush or deform (bend). This bumper reinforcing material is also called bumper reinforcement or bumper armature.

  The bumper reinforcing member and a side member (side frame) on the vehicle body side are formed of a rectangular cylinder having the longitudinal direction of the automobile body as an axial direction, and the collision load of the automobile body is applied in the axial direction. In many cases, a crash box (energy absorbing member) such as a bumper stay that receives and deforms and absorbs collision energy is interposed. This crash box also has a role as a support member (vehicle body connection member) from the rear surface (back surface) of the bumper reinforcement.

  In addition, the deformation accompanying the energy absorption of such a crush box is referred to as a crushing deformation, a crushing deformation, a compressive deformation, a plastic deformation, a buckling deformation, etc. These are deformations (hereinafter these are collectively referred to simply as crushing deformations).

  Conventionally, an aluminum alloy is often used as a material for the bumper reinforcement and the crash box instead of steel for the purpose of reducing the weight of an automobile body for the purpose of reducing the environmental load. However, the aluminum alloy material is more expensive than the steel material, and there is a problem that the cost of manufacturing the automobile body increases.

  Therefore, in order to reduce the cost of manufacturing an automobile body, the bumper reinforcing material is an aluminum alloy extruded hollow shape with good impact energy absorption, but the crush box (bumpy stay) that supports this from the rear side is made of steel. It is necessary to select materials such as

  Here, as in the case of the bumper reinforcement, the crash box is naturally required to have good impact energy absorption. However, in the case of a crash box that is crushed and deformed in the axial direction, lateral crushing in the cross-sectional direction is performed. Energy absorption performance different from the bumper reinforcement is required.

  That is, the crash box is required to have a small load fluctuation at the time of collision in order to efficiently absorb collision energy in a narrow region (stroke). In order to reduce this load fluctuation, it is first necessary to perform a crushing deformation in the axial direction with a small initial load of collision (initial peak load). Next, in the middle of the crushing deformation within the stroke range, there is no decrease (falling) in the load after the middle of deformation due to bending or breakage of the deforming cylinder, continuous crushing deformation, constant collision It is necessary to keep the amount of energy absorption stably.

  In recent years, along with the strengthening of collision safety standards, such high energy absorption performance has been required for crash boxes such as the bumper stay. When the deformation load of the crash box exceeds the load limit (when the maximum load at the time of crushing is too high), the parts such as the side member constituting the vehicle body are deformed earlier than the bumper stay. In addition, even when the bumper stay cannot absorb energy within a limited stroke, there is a problem that parts such as a side member, a radiator, and an engine located behind the damage are damaged.

  As a conventionally known method for suppressing an excessive increase in the initial peak load of the crash box, an emboss (unevenness) or a hole, which is a fragile part for promoting the start of the crushing deformation, is often provided (Patent Documents) 1, 2, 3).

  On the other hand, a method of shortening the buckling wavelength at the time of crush box crushing is effective for suppressing the drop of the load after the latter stage during the crushing deformation. As this method, it is proposed that the cross-sectional shape of the cylinder constituting the crash box is a cross shape extending in all directions (Patent Document 4), or that the cylinder constituting the crash box has a double structure (Patent Document 5). Has been. Moreover, although it is an aluminum alloy extruded hollow shape, there is known a method in which a cross-shaped medium rib is provided in the hollow portion, and these medium rib members are brought into contact with each other to suppress a decrease in load (patent) Reference 6).

  On the other hand, the left and right side members (side frames) of the automobile body to which the bumper reinforcing material is joined via the crash box are also a kind of crash box. That is, as a cylindrical member, at the time of a collision of the vehicle body, it is crushed and deformed with the longitudinal direction of the vehicle body as the axial direction to absorb the collision energy.

  For this reason, conventionally, various structures have been proposed in which various reinforcements are provided in the hollow portions of the side members in order to increase the impact force absorbing ability of these side members. Among these, particularly, in Patent Document 7, the reinforcement is constituted by a steel plate arranged horizontally across the width direction in the side member space, and the reinforcement is easily collapsed integrally with the side member. Thus, it has been proposed not to increase the initial peak load. In this conventional technique, a plurality of holes (through holes) for promoting the crushing deformation are connected in the longitudinal direction of the reinforcement to suppress the amount of load drop after the initial peak load.

  Further, the end position of the flat reinforcement on the front side of the vehicle body is shifted from the end position of the side member on the front side of the vehicle body toward the rear side of the vehicle body, thereby causing a collision from the front side of the vehicle body. When a load is applied, first, the side member starts to collapse in the axial direction, and after a certain time delay, the flat reinforcement then starts to collapse in the axial direction. . After that, both parts collapse in the longitudinal direction of the vehicle body, and the initial peak load is reduced by the time delay of the flattening start of the flat reinforcement, and the drop in load drop after the initial peak load is reduced. Is reduced.

JP 2006-62558 A JP 2005-1462 JP 2002-155980 A JP 2009-83686 Japanese Patent No. 4271929 JP 2006-335241 A JP 2006-62558 A

  However, when providing a fragile portion as a method of suppressing an excessive increase in the initial peak load, the amount of energy absorption per unit weight is reduced because the fragile portion is provided, and a predetermined energy absorption amount is ensured. , Crash box weight is needed and gets heavier.

  In addition, the load drop suppression method after the latter half of the deformation described above (Patent Documents 4 and 5) has a large weight increase compared to the original cylinder crash box for the effect, and the original automobile. The weight of the car body cannot be reduced.

  Moreover, although the said patent document 6 can be used for an aluminum alloy extrusion hollow shape material, such a hollow cross-sectional shape cannot be made with steel materials, and cannot be applied to a steel crash box.

  Furthermore, in the above-described conventional side member technology, the axial length, that is, the stroke (deformation region) is significantly shorter than that of the side frame. Cannot show the effect.

  As described above, in the steel crash box, an excessive increase in the initial peak load is suppressed without impeding weight reduction, and a drop in the load after the late stage of deformation immediately after the initial peak load is suppressed. Therefore, high energy absorption performance is required. However, there is no actual crash box that has achieved this sufficiently.

  Therefore, according to the present invention, it is possible to reduce the weight for absorbing the predetermined energy by increasing the amount of energy absorption per weight, and the crash box that can absorb the predetermined energy in a narrow area. The purpose is to provide.

  In order to achieve the above object, the gist of the present invention crash box is a crash box made of a rectangular steel cylinder that absorbs energy by being deformed in the axial direction, which constitutes the steel cylinder. Providing a cross-sectional hat-shaped reinforcing plate from the inside of the hollow portion of the steel cylinder to the other surface, and extending the cross-sectional hat-shaped reinforcing plate to the other three surfaces along the axial direction of the surface. A hollow portion having a smaller diameter than the steel cylinder is formed in the hollow portion by the surface and the cross-sectional hat-shaped reinforcing plate, and the cross-sectional hat-shaped reinforcing plate The tip position in the axial direction is set backward with respect to the tip position in the axial direction of the surface.

  Here, the crash box is a crash box that takes the longitudinal direction of the automobile body as an axial direction and deforms in response to a collision load of the automobile body in the axial direction to absorb collision energy, and the reinforcing plate is provided with the reinforcing plate The surface is a surface located inside the vehicle body with respect to the width direction of the vehicle body, and the reinforcing plate having the cross-sectional hat shape is not in contact with the other three surfaces over the axial direction of the surface. The hollow portion having a smaller diameter than the steel cylinder is formed in the hollow portion by the one surface and the cross-sectional hat-shaped reinforcing plate, and the axial direction of the cross-sectional hat-shaped reinforcing plate is formed in the axial direction. It is preferable that the front end position be set backward with respect to the axial front end position of one surface located inside the automobile body. Moreover, it is preferable that a top plate and a bottom plate are respectively provided at a front end portion and a rear end portion in the axial direction of the steel cylinder of the crash box. Moreover, it is preferable that the said crash box is arrange | positioned as a bumper stay between the bumper reinforcement material and side member of a motor vehicle body.

  The present invention is the same as the prior art in that impact energy at the time of a car body collision is collapsible and deformed in the axial direction of a crash box made of a rectangular cylinder to absorb the collision energy. In addition, a reinforcement (reinforcing plate) is provided inside the hollow of the crash box, and the crash box and the reinforcement are both crushed and deformed in the axial direction to absorb the collision energy.

  However, in the present invention, the reinforcement is used as a reinforcing plate having a hat-shaped cross section, and the reinforcing plate is formed in a rectangular cylindrical body with respect to one surface located inside the vehicle body with respect to the width direction of the vehicle body. Provide. The reinforcing plate is provided so as not to contact three surfaces other than the one surface, and a closed section hollow portion having a smaller diameter than the rectangular cylindrical body is formed in a transverse section of the hollow interior. And Here, the “surface” referred to in the present invention is basically four (four) “walls” constituting the rectangular cylinder, and is expressed as “side” or “flange”. In some cases.

  Further, the axial front end position of the reinforcing plate is moved backward (to the rear side of the vehicle body) from the axial front end position of one surface located on the inner side of the automobile body. It is characterized by being provided.

  When the collision load is applied from the front side of the vehicle body to the front end of the rectangular cylinder by providing the axial front end position of the reinforcing plate as described above, first, the rectangular cylinder without the reinforcing plate The crushing deformation of the tip portion is likely to start. As a result, even if the crushing strength of the crash box in the axial direction is increased by the installation of the reinforcing plate, the initial peak load in the load-displacement characteristic can be prevented from being increased. That is, when a collision load is applied from the front side of the vehicle body, first, the crash box (the tip of a rectangular cylinder without a reinforcing plate) starts to collapse in the axial direction, and then with a certain time delay, In addition to the crash box portion with the reinforcing plate, the hat-shaped reinforcing plate starts to collapse in the axial direction, and thereafter, both of them integrally collapse in the longitudinal direction of the vehicle body (collapsed in a bellows shape).

  Here, in the present invention, the reinforcing plate is provided so as not to contact the other three surfaces, and a small-diameter closed section hollow portion is formed in the hollow interior of the rectangular cylindrical body. For this reason, when a collision load is applied, one surface located inside the vehicle body provided with the reinforcing plate is integrated as a three-dimensional hollow structure, not as a flat wall or a single plate. The energy can be absorbed by crushing deformation. For this reason, in the middle of the crushing deformation, in particular, each surface of the cylindrical body, particularly one surface located inside the automobile body, is prevented from being bent or damaged, and a decrease (drop) in the load after the middle stage of deformation is suppressed. be able to. As a result, the crash box is continuously crushed and deformed within the range of the stroke, and a constant collision energy absorption amount can be stably maintained, and the displacement amount of the crash box, that is, the intrusion amount into the vehicle body. Can be reliably reduced.

It is a perspective view which shows one aspect | mode of this invention crash box. It is aa sectional drawing (transverse sectional view) of FIG. It is a perspective view which shows only the 1st reinforcement board 10 of FIG. It is a perspective view which shows the other aspect of this invention crash box. It is aa sectional drawing (transverse sectional view) of FIG. FIG. 5 is a longitudinal sectional view when a top plate and a bottom plate are respectively provided in FIG. 4. It is a perspective view which shows the aspect which each provided the top plate and the baseplate in the front-end | tip part and rear-end part of the crash box of FIG. It is a longitudinal cross-sectional view of FIG. It is a schematic diagram which shows the aspect provided in the bumper reinforcement material by making the crash box of FIG. 4 into a bumper stay. It is a cross-sectional view which shows the other aspect of this invention crash box. It is a cross-sectional view which shows the other aspect of this invention crash box. It is a cross-sectional view which shows the other aspect of this invention crash box. It is a cross-sectional view which shows the other aspect of this invention crash box. It is a load displacement curve concerning the example of the present invention. It is a load displacement curve concerning the example of the present invention. It is a longitudinal cross-sectional view which shows the conventional crash box. It is a longitudinal cross-sectional view which shows the crush box of a comparative example.

  Embodiments of the present invention will be specifically described below with reference to the drawings. In addition, although this invention is not limited to these embodiment, the following description demonstrates taking the crash box for motor vehicles as an example.

(Cylinder structure)
The embodiment of FIG. 1 is intended for a bump box such as a bumper stay that supports a bumper reinforcement from the rear side, but is drawn without a top plate, and the hollow interior of the cylinder of the present crash box Makes it easy to see. The bumper reinforcement may be used either on the front side (front side) or the rear side (rear side) of the automobile (vehicle body), and any of them can be used. However, the following description is intended for the front side.

  Therefore, when referring to the positional relationship in the front-rear direction of the vehicle body, for example, the term “vehicle body rear side” is read as “vehicle body front side” in the case of the rear side.

  In FIG. 1 and FIG. 2, the hollow cylinder of the crash box of the present invention is premised on a rectangular steel cylinder whose axial direction is the longitudinal direction (vertical direction in the figure) of the automobile body indicated by the alternate long and short dash line in FIG. It consists of two. 1 receives the collision load of the automobile body indicated by the arrow in FIG. 1 and deforms into a bellows shape in the axial direction to absorb the collision energy.

  Here, the steel cylinder 2 shown in FIG. 1 is formed in such a manner that the U-shaped members 3 and 4 face each other, and the end portions of each surface (flange) in the U-shape are overlapped and welded together. , Integrated into a hollow rectangular cylindrical shape. The U-shaped members 3 and 4 are well-known steel materials manufactured by press-forming steel plates, but rolled steel shapes or the like may be used.

  The axial lengths (heights in FIG. 1) of the members 3 and 4 in FIGS. 1 and 2 are different from each other, and the surfaces 5 and 6 (walls 5 and 6) extending in the width direction of the vehicle body. On the other hand, the front ends (upper side in FIG. 1) of the surfaces 7 and 8 (walls 7 and 8) extending in the width direction of the automobile body are inclined upward in FIG. This is because the bumper reinforcement conforms to the design shape of the bumper and curves (inclined) to the rear (front side) or front (rear side) of the car body in the width direction of the car body at a certain bending angle. ).

  The crash box in FIG. 1 shows a crash box located on the left side of the two left and right sides toward the upper side (vehicle body front end side) in FIG. The bumper reinforcement supported by the crash box is inclined upward toward the upper side (the front end side of the vehicle body) in FIG. For this reason, in the curved (inclined) portion of the bumper reinforcing material, the crush box supported from the rear surface side is also adapted to the curved (inclined) shape of the bumper reinforcing material as described above. The tip (upper side in FIG. 1) is inclined upward in FIG. That is, the member 3 (surface 5) located inside the automobile body is located outside the automobile body with respect to the width direction of the automobile body (the right-and-left direction in FIG. 1 and the vertical direction in FIG. 2). Longer than the member 4 (surface 6). Further, since the rear end or the end of each surface (the lower side in FIG. 1) are made to coincide, the position of the tip 6a of the shorter surface 6 is closer to the rear of the vehicle than the position of the tip 5a of the longer surface 5. Retreating.

  In addition to this FIG. 1, the hollow cylinder body of this crush box has the method of making by the combination and joining of various cross-sectional steel materials as shown in FIGS. . 10 and 11 show hat-shaped (HAT-type) cross-sectional members 3, 4 facing each other, and the flanges 3a and 4a are joined together by welding to be integrated into a hollow cylindrical shape. . FIGS. 12 and 13 show a hat-shaped (HAT-type) cross-sectional shape of the member 4, and the end of the flat member 3 is welded to the flange 4 a of the member 4 to form a hollow cylindrical body. It is an integrated one.

  Steel materials (steel plates) used for the hollow cylinder of this crash box are selected from steels (steel plates) of various strength classes from ordinary steel and mild steel to high tensile strength, depending on the strength required for each vehicle type. Even a normal galvanized steel material (steel plate) may be a steel material (steel plate) coated with resin. As described above, when the bumper reinforcing material is made of an aluminum alloy extruded hollow shape, when the crush box (bumper stay) that supports this from the rear side is made of steel, it is particularly preferable for electrolytic corrosion due to dissimilar material joining. Corrosion measures are required. For this reason, it is preferable that at least the portions in contact with the aluminum alloy extruded hollow member are insulated from each other by resin coating.

(Reinforcement plate structure)
Considering the offset collision of the automobile in particular, when the collision load applied to the bumper reinforcement is propagated from the rear surface side to the tip of the crash box, each surface of the cylindrical body constituting the crash box 5, 6, 7, and 8 are loaded unevenly. That is, when the bending angle (curvature) of the installed bumper reinforcing material increases, a load is input from the bumper reinforcing material on the inner side in the vehicle body width direction from the crash box due to the collision load applied to the bumper reinforcing material.

  Therefore, in the case of such a collision mode, of the surfaces (walls) 5, 6, 7, and 8 constituting the rectangular cylindrical body, the width direction of the vehicle body indicated by the arrows in FIGS. The load is most applied to the surface 5 (one surface 5 or the wall 5) located on the inner side of the automobile body with respect to the right-and-left upward direction and the vertical direction in FIG. For this reason, it becomes easy to generate | occur | produce the fall (drop) of the load after the said middle stage of a deformation | transformation by the bending of this surface 5, or damage.

  Therefore, it is important to reinforce this most loaded surface 5. However, as a means for reinforcing this surface 5, a method of increasing the thickness of this surface 5 can be considered in common sense. As a method of increasing the thickness, there is a method of joining the reinforcing plate to the surface 5 from the inside of the hollow portion or from the outside, and only the thickness of the surface 5 (plate thickness) is the thickness of the other surface (plate). There is also a method of making it larger than (thickness). However, in these methods, reinforcement by increasing the thickness does not lead to an improvement in the amount of collision energy absorbed for an increase in weight. In addition, excessive reinforcement due to the increase in thickness causes a problem that the peak load at the initial stage of deformation cannot be suppressed and stable energy absorption cannot be obtained.

  On the other hand, in the present invention, as shown in FIGS. 1 and 2, as described above, the hollow surface of the steel cylinder 2 with respect to the surface 5 to which the most load is applied (to the inner surface side in FIG. 5). A first reinforcing plate 10 having a hat-shaped cross section is provided from the inside of the part A. In the present invention, the cross-sectional shape of the first reinforcing plate 10 and the way in which the first reinforcing plate 10 is provided along the axial direction of the surface 5 are particularly important.

Reinforcing plate cross section:
Only the first reinforcing plate 10 shown in FIGS. 1 and 2 is taken out and shown in a perspective view in FIG. In the reinforcing plate 10, a flat portion 12 extending in the axial direction and surfaces 13 and 14 projecting from both side surfaces of the flat portion 12 to form a wide end form a U-shaped member. Then, flat flanges 13a and 14a each extending from the surfaces 13 and 14 to the sides are added, and a reinforcing member structure having a hat shape (HAT shape) in cross section is provided.

  Such a hat-shaped cross-sectional shape is formed in the hollow portion A of the steel cylinder 2 (within the transverse cross section of the hollow portion A), the surface 5 which is a flat wall of the cylinder 2 and the first reinforcing plate 10. Thus, it is optimal for forming the second closed hollow portion B having a smaller diameter than the steel cylinder 2. As shown in FIGS. 1 and 2, such a second closed hollow portion B is made independent of the other three surfaces 6, 7, 8 of the steel cylinder 2 other than the surface 5 ( It is provided over the axial direction of this surface 5 (separated). Accordingly, the surface 5 to which the load is most applied is not a planar reinforcement that increases the thickness but a hollow structure (closed section hollow portion), and is reinforced as a three-dimensional hollow structure.

  For this reason, when a collision load is applied, the surface 5 is not a planar wall or a single plate, but a three-dimensional integral hollow structure composed of the first reinforcing plate 10, Energy is absorbed by crushing deformation. That is, the surface 5 located on the inner side of the vehicle body provided with the first reinforcing plate 10 can be integrally collapsed and absorb energy as a three-dimensional hollow structure.

  Therefore, it is possible to prevent bending and breakage when the surface 5 is thin and planar, and to suppress a decrease (drop) in load after the latter stage of deformation during crushing deformation. As a result, the crash box is continuously crushed and deformed within the range of its stroke, and it is possible to continue to secure a certain amount of collision energy absorption, ensuring the amount of displacement of the crash box, that is, the amount of penetration into the vehicle body. Can be reduced.

  If the first reinforcing plate 10 is provided so as to be in contact with the three surfaces 6, 7, 8 of the steel cylinder 2 other than the surface 5, the interference of the other three surfaces 6, 7, 8 is caused. In response, the hollow structure cannot be crushed and deformed independently. Moreover, since the steel tube 2 itself is less likely to be crushed and deformed in the same manner as providing a rib in the mouth-shaped cross-section hollow part A itself of the steel tube 2, the peak load at the initial stage of deformation is reduced. Cannot be suppressed, and stable energy absorption cannot be obtained.

Reinforcing plate installation position:
The length (installation position) of the first reinforcing plate 10 is in the axial direction of the surface 5 in order to exert (guarante) the reinforcing effect as the hollow structure over the axial direction of the surface 5. It is preferable that the rear end (end) is substantially coincident with the rear end (end) of the surface 5.

  However, as shown in FIG. 1, the axial front end position 10a of the first reinforcing plate 10 is longer than the axial front end position 5a of the surface 5 (one surface 5) by a length L1, as shown in FIG. It is important to set it back (shifted) to the side (the front side of the vehicle body on the rear side). When the front end position 10a in the axial direction of the first reinforcing plate 10 is retracted as described above, when a collision load is applied to the front end portion 2a of the rectangular cylindrical body 2 from the front side of the vehicle body, first, the reinforcing plate It becomes easy to start the crushing deformation of the distal end portion 2a of the rectangular cylinder 2 without 10. As a result, even if the crushing strength in the axial direction of the crash box 1 is increased by installing the first reinforcing plate 10, the initial peak load in the load-displacement characteristic can be prevented from being increased.

  That is, when a collision load is applied to the front end portion 2a of the rectangular cylindrical body 2 from the front side of the vehicle body, first, the crash box (the front end portion 2a of the rectangular cylindrical body 2 without the reinforcing plate) starts to collapse in the axial direction. Next, with a certain time delay, the crush box part at the position where the first reinforcing plate 10 is located and the first reinforcing plate 10 forming the hollow structure start to collapse in the axial direction. , Crushing deformation in the longitudinal direction of the car body (crushing in a bellows shape). As a result, when a collision load is applied from the front side of the vehicle body, in the middle of the crushing deformation, in particular, each surface of the cylindrical body, in particular, one surface located inside the automobile body is prevented from being bent and damaged. It is possible to suppress a decrease (drop) in the load after the latter period. Therefore, the crash box continuously crushes and deforms within the range of the stroke, and it is possible to stably keep a certain amount of collision energy absorption, and the amount of displacement of the crash box, that is, the amount of intrusion into the vehicle body can be reduced. It can be reliably reduced.

  On the other hand, the comparative example shown in FIG. 17 is provided with the reinforcing plate 10 according to the present invention, but the axial tip position 10a of the reinforcing plate 10 is referred to as the axial tip position 5a of the surface 5. It is set as the same position (level), and it is not made to retreat to the back side rather than the 5a. In this case, since the reinforcing plate 10 is necessarily provided and reinforced, the initial peak load is significantly increased as compared with the present invention, and the stable energy absorption characteristic cannot be obtained.

  The size of the “retraction length L” (“shift length L”) of the tip position 10a in the axial direction of the reinforcing plate such as the first reinforcing plate 10 and the second reinforcing plate 11 described later is naturally It depends on the design conditions (size, shape conditions) of the crash box 1. However, as one guideline in the bumper stay, the size of the “retraction length L” for suppressing the increase in the initial peak load is set to the axial length l of the rectangular cylinder (the longer surface 5). The length is selected in the range of l / 10 to l / 2 in relation to the axial length l: mm).

Two reinforcing plates:
4, 5, and 6 show another mode in which two reinforcing plates are provided in the crash box 1. In these drawings, in addition to the aspect in which the first reinforcing plate 10 is provided on the surface 5 of the crash box 1 of FIGS. 1 and 2, the vehicle body is positioned outside the vehicle body with respect to the width direction of the vehicle body. On the surface (one surface) 6 (on the inner surface side in FIG. 6), a second reinforcing plate 11 having a similar hat shape is provided.

  The function expected of the second reinforcing plate 11 with respect to the surface 6 is the same as that of the first reinforcing plate 10, and therefore the method of providing the same is also the same as that of the first reinforcing plate 10. That is, it is further provided along the axial direction of this one surface 6 so as not to contact the three surfaces 5, 7, 8 other than this surface 6, and in the hollow portion A (within the transverse section of the hollow portion A). In addition, the third closed cross-section hollow portion C having a smaller diameter than the rectangular cylinder is further formed by the one surface and the second reinforcing plate 11.

  Then, the axial tip position 11a of the second reinforcing plate 11 is moved backward by L2 from the axial tip position 6a of the surface 6 located on the inner side of the automobile body. At this time, as described above, the position of the front end 6a of the surface 6 is set backward from the position of the front end 5a of the surface 5 to the vehicle body rear side.

  1 and 2 are advantageous when the bending angle of the bumper reinforcement is large, but on the other hand, depending on the vehicle type, the bending angle (degree of curvature and inclination) of the bumper reinforcement is smaller by design. In some cases. In this case, a load is input to the crash box also from the bumper reinforcing material outside the vehicle body from the crash box. In such a case, a large load is gradually applied to the surface (one surface) 6 positioned outside the vehicle body with respect to the width direction of the vehicle body. Therefore, the same effect as that of the reinforcing plate 10 can be achieved by reinforcing the reinforcing plate 11 in the same manner as the surface 5 located on the inner and outer sides of the automobile body.

Reinforcing plate production:
These reinforcing plates 10 and 11 are well-known steel materials manufactured by press-molding steel plates in the same manner as the steel cylinder 2, but rolled die steel or the like may be used. The steel material (steel plate) used for this reinforcing plate is also of various strength classes from ordinary steel and mild steel to high tensile strength depending on the strength required for each vehicle type, as with the steel cylinder 2. Steel (steel plate) is selected, and it may be a normal galvanized steel material (steel plate) or a resin-coated steel material (steel plate).

Crash box installation:
FIG. 9 shows a state in which the crash box 1 of FIGS. 7 and 8 is attached as a bumper stay that supports the bumper reinforcing material from the rear side. 7 and 8 show a mode in which a top plate 16 and a bottom plate 15 are provided at the front and rear ends of the steel cylinder 2 shown in FIGS.

  The top plate 16 conforms to the inclined shape on the front end side of the steel cylinder 2 and is joined to the front end side of the steel cylinder 2 so as to be separated from each other with cuts and flanges 16a and 16b. , 16c, 16d are superposed on the outer surface of the tip of each surface 5, 6, 7, 8 of the steel cylinder 2 and joined by welding or the like. On the other hand, the bottom plate 15 is a flat plate, and is joined to the rear end portions of the surfaces 5, 6, 7, 8 of the steel cylinder 2 by welding or the like.

  As shown in FIG. 9, the top plate 16 is joined to the rear wall 17 of the left bumper reinforcement member by welding or the like toward the front end of the vehicle body. The bottom plate 15 is joined to the front wall 18 of the side member on the left rear side of the vehicle body by welding or the like. Of course, these joints may be mechanical joints such as bolts, or a combination of these mechanical joints and weld joints.

  Examples of the invention shown in FIGS. 1, 2 and 4 (however, in actuality, the models shown in FIGS. 7, 8 and 6 in which the top plate 16 and the bottom plate 15 are provided) are used as the crash boxes assuming the bumper stay supporting the curved bumper reinforcement. 16) as a comparative example and a conventional embodiment of FIG. 16 were modeled, and the deformation mode (load-displacement relationship) and the amount of energy absorption when compressively deformed in the axial direction were obtained by FEM analysis.

  As a result of these, the load / weight-displacement curves of the respective examples are shown in FIGS. 14 and 15, and the energy absorption amount at the weight and displacement of 80 mm and the energy absorption amount per weight are shown in Table 1.

Here, the comparative example (conventional example) of FIG. 16 differs only in that the reinforcing plate 10 according to the present invention is not provided, and the other conditions are the same as those of the inventive example. Table 2 shows the size and shape conditions of the crash box of each of the invention examples and comparative examples. The material of the rectangular cylinder and the reinforcing plate was commonly a 440 MPa grade steel plate (HITEN). Moreover, the top plate 16 and the bottom plate 15 were also made of the same 440 MPa grade steel plate, and the plate thickness was set to 3.2 mm in common. For the FEM analysis, general-purpose finite element method analysis software LS-DYNA was used. In this analysis, the shape factor of the top plate 16 and the bottom plate 15 was set such that the area of the top plate 16 was 18694 mm ² and the area of the bottom plate 15 was 23614 mm ² .

  As can be seen from Table 1 and FIG. 14, each of the inventive examples has an energy absorption amount and an energy absorption amount (load) per weight higher than that of the comparative example, confirming the effect of improving the stable energy absorption characteristics of the present invention. can do.

  Further, among Invention Examples, Invention Example 2 in which two reinforcing plates are installed has a higher load per weight than Invention Example 1 in the case of one. Further, from the comparison of the load / weight-displacement curves of Invention Example 2 and Invention Example 1 in FIG. 14, even if a reinforcing plate is provided (increased), the initial peak load does not increase, and after the initial peak load. It is possible to prevent the drop of the load drop and increase it, and it is proved that the effect of improving the stable energy absorption characteristics can be obtained.

  Further, the load / weight-displacement curves of the invention example 3 and the invention example 4 in which the retreat length L from the axial front end position 5a of the first reinforcing plate 10 from the axial front end position 5a is different. Is shown in FIG. As can be seen from FIG. 15, the increase in the initial peak load is larger in the invention example 3 in which the length of the backward movement L is smaller than in the invention example 4 in which the length of the backward movement L is large. The increase in peak load is suppressed as compared with Invention Example 3. Therefore, the axial tip positions of the reinforcing plates 10 and 11 for suppressing the increase in the initial peak load are moved backward (shifted) by the length L toward the rear side of the vehicle body (the front side of the vehicle body at the rear side). ) The importance of providing is supported.

  Thus, from the result of Invention Example 3 in which the amount of retraction at the tip position in the axial direction of the first reinforcing plate 10 is small (small), the amount of retraction is less (not) than in Example 3 of the present invention as shown in FIG. The comparative example inevitably increases the initial peak load significantly more than the invention example 3, and the stable energy absorption characteristic cannot be obtained. That is, in the comparative example shown in FIG. 17, the reinforcing plate 10 according to the present invention is provided, but the axial tip position 10 a of the reinforcing plate 10 is the same position as the axial tip position 5 a of the surface 5. (Level), and there is no retreat of the tip position 10a in the axial direction of the first reinforcing plate 10.

  From the above results, as a crash box, even when assuming a bumper stay that supports the curved bumper reinforcing material and the offset collision loaded thereon, depending on the degree of curvature of the bumper reinforcing material, The critical technical significance of the requirements of the present invention for obtaining stable energy absorption characteristics is supported.

  According to the present invention, it is possible to reduce the amount of drop in load drop immediately after the initial peak load without increasing the initial peak load, and it is possible to provide a crash box with an increased energy absorption amount (average load) per unit weight. . For this reason, the present invention is preferably applied to an automobile crash box (shock absorbing structure) that needs to have both of these required characteristics, and copes with a high-speed collision such as the offset collision. Without increasing complexity, it is possible to reduce the amount of intrusion into the vehicle body in the event of a vehicle collision, and to ensure the safety of the vehicle.

1: Crush box, 2: Steel cylinder, 3, 4: U-shaped member, 5, 6, 7, 8: Surface (or wall), 10, 11: Hat-shaped reinforcing plate, 12: Flat part, 13, 14: Surface, 15: Bottom plate, 16: Top plate, 17: Bumper reinforcement, 18: Side frame,

Claims (4)

  A crash box made of a rectangular steel cylinder that absorbs energy by being deformed in the axial direction, from the inside of the hollow portion of the steel cylinder with respect to any surface constituting the steel cylinder Including a cross-sectional hat-shaped reinforcing plate, and the cross-sectional hat-shaped reinforcing plate is provided so as not to contact the other three surfaces in the axial direction of the surface. A hollow portion having a smaller diameter than the steel cylinder is formed in the hollow portion by the shape of the reinforcing plate, and the axial tip position of the cross-sectional hat-shaped reinforcing plate is defined in the axial direction of the surface. A crash box, which is provided to be retracted rearward from the tip position.   The crash box is a crash box in which the longitudinal direction of the automobile body is an axial direction, and receives the collision load of the automobile body in the axial direction to deform and absorb the collision energy, and the surface on which the reinforcing plate is provided is the crash box It is a surface located inside the vehicle body with respect to the width direction of the vehicle body, and the cross-sectional hat-shaped reinforcing plate is provided so as not to contact the other three surfaces along the axial direction of the surface. Thus, a hollow portion having a smaller diameter than the steel cylinder is formed in the hollow portion by the one surface and the cross-sectional hat-shaped reinforcing plate, and the tip end position in the axial direction of the cross-sectional hat-shaped reinforcing plate is defined. The crash box according to claim 1, wherein the crash box is provided so as to be retracted rearward from a tip position in the axial direction of one surface located inside the automobile body.   The crash box according to any one of claims 1 and 2, wherein a top plate and a bottom plate are respectively provided at a front end portion and a rear end portion in the axial direction of the steel cylinder of the crash box.   The crash box according to any one of claims 1 to 3, wherein the crash box is disposed as a bumper stay between a bumper reinforcement member and a side member of an automobile body.

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