JP4389848B2 - Load energy absorber - Google Patents

Description

  The present invention relates to a load energy absorbing material that absorbs load energy.

  The load energy absorbing material constituting the bumper device that reduces the impact at the time of the collision of the vehicle absorbs the energy of the impact load applied to the bumper reinforcement forming the bumper device. In order to reduce the weight of such a load energy absorbing material, one in which the load energy absorbing material is formed of a fiber reinforced resin is known (for example, see Patent Document 1).

  Patent Document 1 discloses a cylindrical load energy absorbing material. The cylindrical load energy absorbing material is formed by resin transfer molding (resin injection molding). That is, the load energy absorbing material is formed by pressing a thin fiber material into a cylindrical shape by press working, and impregnating the resin into the fiber cylindrical material in the mold.

  However, in the formation of a cylindrical (closed cross-section) load energy absorbing material, it is necessary to form a cylindrical shape using a mold (core) for forming the inner surface of the cylinder. Therefore, in resin transfer molding using a mold (core), compared to resin transfer molding that does not use a mold (core), there is a problem that the number of man-hours for molding increases because of the process for handling the mold (core). There is.

  Patent Document 1 discloses a load energy absorbing material having a U-shaped cross section (an open cross section having one groove). Such an open cross-section load energy absorbing material is easier to manufacture than a cylindrical load energy absorbing material.

  As the load energy absorbing material, an open cross-sectional shape having two grooves extending in the longitudinal direction is also conceivable. Such a load energy absorbing material having an open cross-sectional shape can reduce the groove depth and less likely to bend the side wall of the groove as compared with a U-shaped load energy absorbing material (open cross-sectional shape having one groove). Excellent in holding function of cross-sectional shape. That is, a load energy absorbing material having an open cross-sectional shape having a plurality of grooves is superior in load energy absorption capability compared to a U-shaped load energy absorbing material.

These load energy absorbing materials having an open cross-sectional shape are joined by screwing their ends to the bumper reinforcement. Usually, screwing is performed in two places.
JP-A-6-307479

  In a load energy absorbing material having an open cross-sectional shape having two grooves, if a load in a direction oblique to the length direction of the groove is applied to the load energy absorbing material, the load energy absorbing material is likely to be twisted. When stress concentration occurs in the load energy absorbing material due to twisting of the load energy absorbing material, breakage (cracking) may occur at the stress concentration portion. This breakage is likely to occur at the end of the load energy absorbing material (near the end of the groove). When such breakage occurs, force is transmitted from two screwed parts to the two cross-sections with the break as a boundary. (Transmission of impact load) is performed.

  Assuming that the separate screwed portions are in the portions corresponding to the two outer grooves, the two cross-sectional portions try to twist and deform separately. The initial breakage is promoted by the separate twist, and a crack runs in the longitudinal direction of the energy absorbing material from the initial breakage site at the portion between the two grooves. When cracking is promoted, the load energy absorbing material becomes a structure having two cross-sectional shapes each having one groove, not a structure having one cross-sectional shape having two grooves. Compared to one cross-sectional shape having two grooves, a cross-sectional shape having only one groove is a shape that is easily buckled. That is, a structure in which a crack is formed in a portion between two grooves is an unstable structure in which buckling is likely to occur.

  If there is no crack in the part between the two grooves, buckling will not occur and the load energy absorbing material will break sequentially, but if there is a crack in the part between the two grooves, the load energy absorption Unintentional fracture behavior, such as the material breaking in the middle, may occur. In fracture behavior such as breaking in the middle, load energy absorption capability is low and unstable fracture occurs. Therefore, it is desired to prevent the initial breakage (cracking) that causes the unstable breakage.

  An object of the present invention is to prevent early damage in a load energy absorbing material having an open cross-sectional shape and a cross-sectional shape.

  The present invention has a beam portion whose cross-sectional shape is an open cross-sectional shape, and a mounting portion provided at an end portion of the beam portion, and is loaded with a load in a direction perpendicular to the cross-section of the beam portion. A load energy absorbing material that absorbs energy is targeted, and the invention according to claim 1 divides the cross-sectional shape of the beam portion into a plurality of positions for fixing the mounting target of the load energy absorbing material and the mounting portion. It is a shear center regarding each section cross-sectional shape part, It is characterized by the above-mentioned.

  The load applied to the attachment target is transmitted to the load energy absorbing material through the fixed position. Assuming that this load caused initial breakage in the load energy absorber, the shear center for each of the plurality of cross-sectional shape sections obtained by dividing the cross-sectional shape of the beam section from the position of the initial breakage is obtained by calculation. be able to. The shear center is a position where no rotational deformation (twist deformation) occurs in the load energy absorbing material even when a load is applied. Since a fixed position is provided at the shear center thus obtained, initial breakage is not promoted.

  In a preferred example, the beam portion has at least two grooves provided in parallel, and the cross-sectional shape of the groove forming wall forming each groove is the segmented cross-sectional shape portion or the segmented cross-sectional shape portion. It is a part.

  A load energy absorbing material having an open cross-sectional shape having a plurality of grooves has an excellent ability to absorb load energy. A load energy absorbing material having an open cross-sectional shape excellent in load energy absorption capability is suitable as an application target of the present invention.

  In a preferred example, the groove includes a first groove and a second groove, and the beam portion includes a first sectioned cross-sectional shape portion including the first groove, and the second groove. The fixing means is fixed at the respective shear centers with respect to the first divided cross-sectional shape portion and the second divided cross-sectional shape portion.

  In the load energy absorbing material having an open cross-sectional shape having two grooves in parallel, it is easy to specify a load stress concentration portion, and it is possible to appropriately specify a plurality of two divided cross-sectional shape portions to be divided.

In a preferred example, the load energy absorbing material is made of fiber reinforced resin.
The fiber reinforced resin is hard and brittle and breaks (breaks) without plastic deformation. A load energy absorbing material made of fiber reinforced resin having such properties is suitable as an application target of the present invention.

  In a preferred example, the attachment object is a bumper reinforcement that constitutes a bumper device for mitigating an impact at the time of a vehicle collision. The load energy absorbing material fixed to the bumper reinforcement and the bumper reinforcement Constitutes the bumper device.

  The load energy absorbing material constituting the bumper device is suitable as an application target of the present invention.

  INDUSTRIAL APPLICABILITY The present invention has an excellent effect that it is possible to prevent the initial damage from being promoted in a load energy absorbing material having an open cross-sectional shape and a cross-sectional shape.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1A, load energy absorbing materials 12, 13 made of fiber reinforced resin are fastened to both ends of the bumper reinforcement 11 by bolts 14, 14A and nuts 15, 15A. Since the load energy absorbers 12 and 13 have the same configuration, only the load energy absorber 12 will be described below.

  As shown in FIGS. 1B and 1C, the load energy absorbing material 12 includes a beam portion 16 and an attachment portion 17 integrally formed with one end portion 161 of the beam portion 16. The attachment portion 17 is formed in a flat plate shape orthogonal to the longitudinal direction of the beam portion 16, and a pair of screw-through holes 171 and 172 are provided through the attachment portion 17. The bolt 14 is passed through the screw through hole 171 and screwed into the nut 15, and the bolt 14 </ b> A is passed through the screw through hole 172 and screwed into the nut 15 </ b> A. The load energy absorbing member 12 is fastened and fixed to the bumper reinforcement 11 by fastening the bolt 14 and the nut 15 and fastening the bolt 14A and the nut 15A. The load energy absorbing member 12 absorbs load energy of a load in a direction perpendicular to the cross section of the beam portion 16.

  The cross-sectional shape of the beam portion 16 is an open cross-sectional shape having a first groove 18 and a second groove 19 provided in parallel. The flat plate-shaped attachment portion 17 includes flat plate-shaped side walls 182 and 183 that form side surfaces of the grooves 18 and 19 and end portions of the flat plate-shaped bottom walls 181 and 191 that form the bottoms (planar shapes) of the grooves 18 and 19. , 192, 193 are connected to the end portions of the grooves 18, 19 from the outside. In other words, the mounting portion 17 projects from the ends of the bottom walls 181 and 191 and the ends of the side walls 182, 183, 192 and 193 to the outside of the grooves 18 and 19. The screw through hole 171 is formed at a position close to the connecting portion 173 between the bottom wall 181 of the first groove 18 and the attachment portion 17, and the screw through hole 172 is attached to the bottom wall 191 of the second groove 19. It is formed at a position close to the connecting portion 174 with the portion 17. The bottom wall 181 and the side walls 182 and 183 constitute a groove forming wall that forms the groove 18, and the bottom wall 191 and the side walls 192 and 193 constitute a groove forming wall that forms the groove 19.

  The load applied to the bumper reinforcement 11 to which the load energy absorbing material 12 is attached is transmitted to the load energy absorbing material 12 through the bolts 14 and 14A and the nuts 15 and 15A. For example, an impact load in the direction indicated by an arrow R in FIGS. 1A and 1C may be applied to the bumper reinforcement 11. This is a case where the bumper reinforcement 11 is under the collision object. When an impact load in the direction indicated by the arrow R is applied to the bumper reinforcement 11, a force that twists the load energy absorbing material 12 works, and a specific point Q in the connection portion between the beam portion 16 and the attachment portion 17 [in FIG. Load stress (stress with respect to load) concentrates on the drawing. Therefore, when an impact load of such a magnitude that the load energy absorbing material 12 is broken is applied, it is expected that a crack is first generated in the specific portion Q.

  As shown in FIG. 1 (b), the cross-sectional shape of the load energy absorbing material 12 is divided into the first section cross-sectional shape portion G1 and the second section crossing at a specific location Q where load stress is considered to be concentrated. When divided into the surface shape portion G2, the formation position of the screw through hole 171 is provided at the shear center C1 related to the first section cross-sectional shape portion G1. That is, when viewed in the direction of the grooves 18 and 19 (longitudinal direction of the beam portion 16), the shear center C1 is in the screw hole 171. The screw through hole 172 is provided at the shear center C2 with respect to the second sectioned cross-sectional shape portion G2, and when viewed in the direction of the grooves 18 and 19 (longitudinal direction of the beam portion 16), the shear center C2 is , In the threaded hole 172.

  The bolt 14 and the nut 15 constitute a first fixing means provided at the shear center C <b> 1 related to the first section cross-sectional shape portion G <b> 1 corresponding to the first groove 18. The bolt 14 </ b> A and the nut 15 </ b> A constitute second fixing means provided at the shear center C <b> 2 related to the second section cross-sectional shape portion G <b> 2 corresponding to the second groove 19. That is, the first fixing means (bolt 14 and nut 15) for fixing the attachment portion 17 to the bumper reinforcement 11 is divided into a plurality of divided cross-sectional shape portions G1 obtained by dividing the cross-sectional shape of the load energy absorbing material 12 into a plurality of portions. , G2 is provided at the shear center C1 related to the first section cross-sectional shape part G1. The second fixing means (bolt 14A and nut 15A) for fixing the attachment portion 17 to the bumper reinforcement 11 is provided at the shear center C2 related to the second sectioned cross-sectional shape portion G2.

  The shear center C1 related to the first section cross-sectional shape portion G1 and the shear center C2 related to the second section cross-section shape portion G2 are, for example, “theory of light structure and its application (above), apple edition, It can be obtained by calculation as described in Japan Federation of Science and Technology, September 14, 1966, P. 85-86, Example 3.

  2A and 2B show a load energy absorbing member 20 in which a flat plate-like attachment portion 21 is integrally formed at the end portion 161 of the beam portion 16. The flat plate-shaped attachment portion 21 is connected to the end portions of the bottom walls 181 and 191 of the grooves 18 and 19 and the end portions of the side walls 182, 183, 192 and 193 of the grooves 18 and 19 from the inside of the grooves 18 and 19. Yes. The screw through holes 211 and 212 are formed in the portion of the mounting portion 21 corresponding to the grooves 18 and 19, and by tightening the bolts 14 and 14A and the nuts 15 and 15A passed through the screw through holes 211 and 212, The attachment portion 21 is fastened and fixed to the bumper reinforcement. Unlike the screw through holes 171 and 172 in the present embodiment, the screw through holes 211 and 212 are at positions far away from the shear centers C1 and C2.

  Also in the load energy absorbing material 20, when an impact load in the direction of the arrow R is applied, the load stress is concentrated on the specific portion Q, and when the impact load is large enough to cause the load energy absorbing material 12 to break. First, it is expected that a crack will first occur in the specific portion Q. When a crack (initial breakage) occurs in a specific portion Q of the load energy absorbing material 20 that the load stress is considered to be concentrated on, the first sectioned cross-sectional shape portion G1 is caused by the action of the load applied to the bumper reinforcement. The load is transmitted mainly via the bolt 14 and the nut 15. Further, due to the action of the load continuously applied to the bumper reinforcement, the load is transmitted mainly to the second sectioned cross-sectional shape portion G2 via the bolt 14A and the nut 15A.

  Since the screw through hole 211 is located at a position far away from the shearing center C1, the load transmitted to the first section cross section G1 through the bolt 14 and the nut 15 is the first section cross section G1. Try to twist and deform. Further, since the screw through hole 212 is located at a position far away from the shear center C2, the load transmitted to the second section cross section G2 via the bolt 14A and the nut 15A is the second section cross section. The part G2 is torsionally deformed. That is, the first segmented cross-sectional shape part G1 and the second segmented cross-sectional shape part G2 of the load energy absorbing material 20 are torsionally deformed separately, and therefore the load energy absorbing material 20 is cracked at a specific location Q. (Initial damage) is encouraged. It is desirable that the load energy absorbing material 20 is sequentially broken from the tip end side (attachment portion 21 side) in order to reduce the impact load (increase the load energy absorption capability). However, if a crack (initial breakage) at a specific point Q of the load energy absorbing material 20 is promoted, the load energy absorbing material 20 cannot be broken sequentially from the front end side, and the load of the load energy absorbing material 20 is reduced. Energy absorption capacity will be extremely reduced.

In the first embodiment, the following effects can be obtained.
(1) In the load energy absorbing material 12 of the present embodiment, since the screw through holes 171 and 172 are provided at the shear centers C1 and C2, the first section cross-sectional shape part G1 of the load energy absorbing material 20 and the first There is no possibility that the two sectioned cross-sectional shape portions G2 are separately subjected to the twisting action. That is, the crack (initial breakage) at the specific location Q of the load energy absorbing material 12 is not promoted, and the load energy absorbing ability of the load energy absorbing material 12 is not reduced.

  (2) In the load energy absorbing material 12 having the two grooves 18 and 19 in parallel, it is easy to identify the load stress concentration portion (specific location Q) where initial breakage (cracking) is most likely to occur. Therefore, the two divided cross-sectional shape portions G1 and G2 that are expected to coincide with the cross-sectional shape portion divided by the initial breakage after the occurrence of the initial breakage (cracking) are appropriately identified.

  (3) In some cases, a compressive load is applied to the load energy absorbing material 12 side, and a tensile load is applied to the other load energy absorbing material 13 side. The load energy absorbing material is applied to the bumper reinforcement 11 by two sets of fixing means, that is, a set of a bolt 14 and a nut 15 corresponding to the first groove 18 and a set of a bolt 14A and a nut 15A corresponding to the second groove 19. The configuration in which the members 12 and 13 are fixed is advantageous in preventing dissociation between the separate load energy absorber 13 and the bumper reinforcement 11.

  (4) Compared with the load energy absorbing material 12 having two grooves 18 and 19, in the load energy absorbing material having only one groove, the depth of the groove needs to be increased. Length increases. If the length of the side wall of the groove in the depth direction of the groove is large, the side wall of the groove tends to bend and the load energy absorption capability is deteriorated. In the load energy absorbing material 12 having two grooves 18 and 19 provided in parallel, the grooves 18 and 19 are shallow, and the side walls 182, 183, 192, and 193 of the grooves 18 and 19 are not easily buckled. That is, the load energy absorbing material 12 having the two grooves 18 and 19 provided in parallel is excellent in load energy absorbing capacity, and the load energy absorbing material 12 having an open cross-sectional shape excellent in load energy absorbing capacity is It is suitable as an application object of the invention.

  (5) The screw through holes 171 and 172 are provided at the shear centers C1 and C2. If the screw hole 171 is provided at the shearing center C1, the fixing means including the bolt 14 and the nut 15 is reliably arranged at the position of the shearing center C1. If the screw through hole 172 is provided at the shear center C2, the fixing means including the bolt 14A and the nut 15A is surely arranged at the position of the shear center C2. The fixing means including the bolts 14 and 14A and the nuts 15 and 15A is simple as a means for connecting and fixing the bumper reinforcement 11 and the load energy absorbing material 12, and is suitable for reliably arranging at the shear center. It is a fixing means.

  (6) The fiber reinforced resin is lighter than metal and is an excellent material having high elasticity and high strength. Moreover, the fiber reinforced resin is a brittle material (hard and brittle material), and breaks (breaks) without plastic deformation. Accordingly, the fiber reinforced resin is suitable as a material for the load energy absorbing material. The load energy absorbing material 12 made of fiber reinforced resin having such properties is suitable as an application target of the present invention.

In the present invention, the following embodiments are also possible.
-You may apply this invention to the load energy absorption material of the open cross-sectional shape in which the 3 or more groove | channel was provided in parallel.

-It is good also as a breakage origin specific part by making fiber density in the specific location Q (load stress concentration part) smaller than another site, or not arrange | positioning a fiber in the specific location Q. FIG.
-It is good also considering a dent and a through-hole as a breakage origin specific part.

-You may connect the attachment part 17 and the beam part 16 using an adhesive agent.
-The surface shape of the bottom of the groove may be a curved surface (concave surface).
-The surface shape of the side surface of the groove may be a curved surface shape.

As a material of the load energy absorbing material, for example, CMC (ceramic matrix composite material) which is a brittle material may be used in addition to the fiber reinforced resin.
-You may fix the attachment object of a load energy absorption material, and the attachment part of a load energy absorption material by rivet fastening.

The technical idea that can be grasped from the embodiment described above will be described below.
[1] The means for fixing the attachment part to the attachment object includes a bolt and a nut for fastening and fixing the attachment part to the attachment object, and a screw thread provided in the attachment part for passing the bolt. The load energy absorbing material according to any one of claims 1 to 5, wherein a hole is provided at the shear center.

  The fixing means including a bolt and a nut is simple as a means for connecting and fixing the object to be attached and the load energy absorbing material, and is a preferable fixing means for accurately arranging at the shearing center.

1A is a plan view of a bumper reinforcement and a load energy absorbing material according to a first embodiment. (B) is the sectional view on the AA line of Fig.1 (a). (C) is a perspective view of a load energy absorber. The load energy absorption material for comparing with the load energy absorption material of 1st Embodiment is shown, (a) is a perspective view. (B) is sectional drawing.

Explanation of symbols

  11 ... Bumper reinforcement as a mounting target. 12, 13 ... Load energy absorbing material. 14: A bolt constituting the first fixing means. 15 ... Nuts constituting the first fixing means. 14A: A bolt constituting the second fixing means. 15A ... Nuts constituting the second fixing means. 16: Beam part. 161: end. 17: A mounting portion. 18 ... 1st groove | channel. 181: A bottom wall constituting a groove forming wall. 182, 183... Sidewalls constituting the groove forming wall. 19: Second groove. 191: A bottom wall constituting a groove forming wall. 192, 193 ... Side walls constituting the groove forming wall. G1: First section cross-sectional shape portion. G2: Second section cross-sectional shape part. C1, C2 ... shear center.

Claims (5)

It has a beam part whose cross-sectional shape is an open cross-sectional shape, and a mounting part provided at an end of the beam part, and absorbs load energy in a direction perpendicular to the cross-section of the beam part. In load energy absorbing material,
The load energy absorbing method, wherein the load energy absorbing material is attached to the attachment portion at a position where the position of fixing the attachment portion is a shear center with respect to each divided cross-sectional shape portion obtained by dividing the cross-sectional shape of the beam portion into a plurality of portions. Wood.   The beam portion has at least two grooves provided in parallel, and the cross-sectional shape of the groove-forming wall forming each groove is the segmented cross-sectional shape portion or a part of the segmented cross-sectional shape portion. The load energy absorbing material according to claim 1.   The groove includes a first groove and a second groove, and the beam portion includes a first section cross-sectional shape portion including the first groove and a second section including the second groove. The fixing means is fixed at each shearing center with respect to the first sectioned cross-sectional shape part and the second sectioned cross-sectional shape part. Load energy absorber.   The load energy absorbing material according to any one of claims 1 to 3, wherein the load energy absorbing material is made of a fiber reinforced resin.   The attachment object is a bumper reinforcement that constitutes a bumper device for reducing an impact at the time of a vehicle collision. The load energy absorbing material fixed to the bumper reinforcement and the bumper reinforcement are the bumper The load energy absorbing material according to any one of claims 1 to 4, constituting the device.

Images