JP2006207679A - Method for manufacturing shock absorbing member - Google Patents

Abstract

An impact absorbing member capable of achieving both a short deformation stroke and excellent energy absorption efficiency is provided.
A hollow impact-absorbing member 1 having a longitudinal direction and a short-side direction and absorbing an impact by bending deformation, wherein a compression site 10 in which a compressive stress is generated by receiving the impact directly. A tensile portion 12 facing the compression portion 10 where a tensile stress is generated, and a pair of side portions 14 connecting both ends of the compression portion 10 and the tensile portion 12, and at least the side portions The part 14 is provided with a bellows-like deformation promoting means 16 composed of a plurality of peaks 162 and valleys 164 having a predetermined radius of curvature, and the deformation promoting means 16 is formed of a fiber reinforced plastic material, and The impact absorbing member 1 is arranged at a position where the top of the trough 164 is inside the line connecting both ends of the deformation promoting means 16 in the longitudinal direction.
[Selection] Figure 1

Description

    The present invention relates to an impact absorbing member, and more particularly to an impact absorbing member capable of achieving both a short deformation stroke and excellent energy absorption efficiency.

  Conventionally, a fiber reinforced material is used in addition to aluminum as a lightweight and high-strength structural member. The fiber reinforced material is a composite material reinforced with fibers, and fiber reinforced rubber (FRR), fiber reinforced metal (FRM), fiber reinforced ceramics (FRC), fiber reinforced plastic (FRP), and the like are known. Of these, FRP, which is most often used as a fiber reinforced material, uses plastic as a matrix (substrate), and it is known that fibers such as carbon and glass are generally used as the reinforcing material. .

  A material using carbon fiber as a reinforcing material for FRP is called carbon fiber reinforced plastic (CFRP). CFRP is located at the core of advanced composite materials, and is known as a lightweight, high-strength, high-modulus material that is indispensable for the aviation and space fields. As the CFRP material, a unidirectional material (UD material) and a cloth material having different structures and properties depending on the orientation of carbon fibers are known. The UD material is a material form in which carbon fibers are arranged in one direction and molded with an epoxy resin or the like. On the other hand, the cloth material is a material form in which fibers such as carbon fibers are woven or knitted and are molded with an epoxy resin or the like. These CFRPs are excellent in heat resistance and corrosion resistance while being light and about 25% of the weight of iron.

  Conventionally, aluminum and aluminum alloy materials, which are lightweight and high-strength structural members, are used as impact absorbing members for automobiles and the like from the viewpoints of protecting passengers and improving fuel consumption. In particular, in beam materials used for automobile side parts such as front pillars, center pillars, and rear pillars, in order to protect passengers from impacts at the time of a collision, an impact absorbing member having a better energy absorption amount is desired. Yes.

  For example, in a frame installed on the side structure material of an automobile, energy absorption at the time of collision is improved by extruding or pressing a single material and making the cross-sectional shape closed and large to increase strength and rigidity. The amount is increased. In general, as a deformation mode at the time of a side collision, if a center pillar is taken as an example, bending deformation by three-point bending, which is bent with an upper side roof rail and a lower side sill as fulcrums, is applied. Therefore, it is desired that the side structure material has a high durability against bending load and a small deflection due to bending.

  Moreover, in the pillar which is a side structure member of a motor vehicle, when an aluminum material or an aluminum alloy material is used, a hollow structure is employed in order to obtain a large moment of inertia of a cross section with the same weight. Such an impact-absorbing member such as aluminum has a property that the load strength decreases rapidly immediately after the load applied by the impact reaches the maximum strength. This means that when the applied load exceeds the yield point, the shock absorbing member is easily deformed with a small load, and therefore once the yield point is exceeded, the deformation amount of the vehicle body is large. That is, when the yield point is exceeded, the load that can be endured is reduced, and a large deformation of the vehicle body is caused by a small load, so that the amount of energy absorption calculated by the product of the load and the displacement is reduced. Therefore, as a shock absorbing member such as a pillar, even if a load near the yield point continues to be applied after the load reaches the maximum strength and exceeds the yield point, the load strength is maintained until a certain displacement is reached. It is desirable to be a thing.

  In this regard, Patent Document 1 discloses a member in which an FRP material is integrated adjacently to the tensile surface side of an aluminum hollow shape. This uses a member that is easily plastically deformed on the compression surface side, and uses a high-strength and lightweight member on the tension surface side, which is responsible for shock absorption on the compression surface side and reduces the amount of surface change on the tension surface side. This is a technology that aims to achieve large energy absorption and small deformation.

Further, in Patent Document 2, a bellows-like load transmitting member is disposed at a location subjected to bending deformation in a vehicle body structural member that absorbs energy by axial crushing, and a ridge line of the folded bellows is used as a load receiving surface. A technique has been disclosed in which the ridgeline of the accordion is used as a coupling portion to a structural member to achieve good axial crushing characteristics and to improve the strength against bending input.
Japanese Patent Laid-Open No. 06-101732 JP 2004-75021 A

  However, since the shock absorbing member disclosed in Patent Document 1 uses aluminum that is easily plastically deformed on the compression side, the amount of energy absorbed by the shock absorbing member is mainly determined by the yield stress on the compression side. End up. That is, the high-strength FRP material on the tension side has a low contribution as an energy absorbing material, and there is a limit to improving the weight efficiency by using aluminum. In addition, since this shock absorbing member has a structure in which aluminum and FRP are joined by bolts, stress concentration occurs at the bolt joints due to deformation due to the load, and this invention has a unique advantage. There is a possibility of breaking from the joint before it can be used. Even if an adhesive is used in place of the bolt, the upper limit of the strength of the entire shock absorbing member is determined by the strength of the adhesive.

  Moreover, when the load transmission member disclosed in Patent Document 2 is adopted as a hollow long material that receives a load, the load transmission member itself acts as a resistance to generate a load, and acts on the long material in a substantially perpendicular direction. The load cannot be converted in the longitudinal direction. FIG. 10 shows a situation in which an impact is applied to the load receiving surface 301 of the load transmitting member disclosed in Patent Document 2. When an impact is applied to the mountain folded portion 302 from the direction of the arrow in FIG. 10 (A), the load transmitting portion disclosed in Patent Document 2 is only crushed in cross section as shown in FIG. 10 (B) due to the impact. Become. FIG. 10C shows a cross-sectional view of the structural member 300 taken along line AA in FIG. In other words, the load transmission member disclosed in Patent Document 2 only contributes to the load by the resistance of the load transmission member itself. After all, the cross-section is crushed by the bending load and cannot withstand the bending moment. Cannot solve the fundamental problem.

  Further, even if the load transmitting member disclosed in Patent Document 2 is connected by bonding, welding, or the like to prevent the cross-section from being crushed, the risk of breakage from the connecting portion increases, and the rigidity of the connection range is increased. As a result, the load fluctuation at the time of compression becomes large, and it may not be possible to improve the shaft crushing characteristics. In addition, this load transmission member is only intended to improve the performance of the axial crushing energy absorbing member, and is not intended for structural members that receive only bending load without receiving load in the axial crushing direction. It does not achieve an improvement in energy absorption performance against deformation alone.

  This invention is made | formed in view of the above subjects, and it aims at providing the impact-absorbing member which can make a short deformation | transformation stroke and the outstanding energy absorption efficiency compatible.

  As a result of intensive research to solve the above problems, the present inventors have provided a bellows-like deformation promoting means at a predetermined position of the hollow impact absorbing member, thereby realizing a short deformation stroke and excellent energy absorption efficiency. As a result, the present invention has been completed. More specifically, the present invention provides the following impact absorbing member.

  (1) A hollow impact absorbing member having a longitudinal direction and a transverse direction and absorbing an impact by bending deformation, and a compression site where a compressive stress is generated by receiving the impact directly, There is a tensile part that is opposed to the compression part and generates a tensile stress, and a pair of side parts that connect both ends of the compression part and the tensile part, and at least the side part has a predetermined radius of curvature. A bellows-like deformation promoting means comprising a plurality of crests and troughs having a shape is provided, the deformation promoting means is formed of a fiber reinforced plastic material, and the top of the trough is the deformation in the longitudinal direction. An impact absorbing member disposed at a position on the inner side of a line connecting both ends of the promoting means.

  The impact absorbing member (1) has a bellows-like structure as a deformation promoting means on the side of a portion that receives an impact. Generally, when a structural member receives an impact, the structural member is bent at a portion where the load portion and the bending moment take extreme values. When a structural member is subjected to bending deformation, a compressive stress is generated in a portion that receives an impact directly, and a tensile stress is generated in a portion opposite to the portion where the compressive stress is generated. When the value exceeds the bending load, the bending load decreases, the compression site buckles, and the cross section collapses.

  In this respect, according to the impact absorbing member of (1), the bellows-like deformation promoting means formed of the fiber reinforced plastic material is provided on the side of the portion that receives the impact. When a load due to is applied, the bellows of the portion where the compressive stress is generated buckles. When a bellows formed of a fiber reinforced plastic material buckles, a constant load is generated. Therefore, the bellows buckling can be stably generated at a portion subjected to compression. In addition, since the load increases due to interference after buckling, the surrounding bellows are further buckled by the force. As a result, the force for crushing the cross section can be continuously converted into the load at the time of buckling of the bellows, and the bending energy absorption efficiency is improved by expanding the deformation around the load portion while maintaining the cross-sectional shape of the load portion. be able to.

  Further, the bellows-like deformation promoting means provided in the shock absorbing member of (1) has a continuous shape in which a plurality of crests and troughs formed with a predetermined curvature are smoothly connected, and more It enables stable bellows buckling. Further, the top of the bellows-shaped valley is disposed at a position inside the straight line connecting both ends of the deformation promoting means in the longitudinal direction, so that the bellows part bulges outward when the bellows buckles, Can be prevented from being crushed.

  (2) The impact absorbing member according to (1), wherein the deformation promoting means is arranged in a direction in which each ridge line of the peak portion and the valley portion is substantially orthogonal to the longitudinal direction.

  According to the shock absorbing member of (2), by arranging the ridge lines of the bellows-like ridges and valleys that serve as the deformation promoting means in a direction substantially perpendicular to the longitudinal direction, A constant load can be generated in both of the tensile parts, energy absorption efficiency can be improved, and the deformation stroke can be shortened.

  (3) The impact absorbing member according to (1) or (2), wherein the radii of curvature of the peaks and valleys are different from each other.

  According to the shock absorbing member of (3), the strength of the load generated during buckling of the bellows can be adjusted by forming the crest and trough with different radii of curvature. Thereby, even if it is a position away from a load point, the area | region which is easy to buckle can be formed, and a deformation | transformation and destruction area | region can be expanded and controlled. Although the curvature radius of a peak part and a trough part is not specifically limited, When the curvature radius of a trough part is smaller than the curvature radius of a peak part, since a side site | part is easy to deform | transform outside at the time of bending deformation of an impact-absorbing member. The cross section swells to the outside of the member, and the section modulus may decrease. On the other hand, when the curvature radius of the trough is larger than the curvature radius of the peak, the bellows of the side part is effectively buckled during bending deformation of the shock absorbing member, and the cross section is outside the member. This is preferable because it does not swell. Moreover, there may be peaks having different radii of curvature, and there may also be valleys having different radii of curvature.

  (4) The impact absorbing member according to any one of (1) to (3), wherein the deformation promoting means provided in the side part is disposed from the compression part side to the compression part side across a neutral axis.

  According to the impact absorbing member of (4), the bellows-like deformation promoting means is disposed from the compression site side to the compression site side across the neutral axis, so that the bellows sits more effectively when an impact is applied. Bow. Therefore, the force for crushing the cross section can continue to be more effectively converted into the load at the time of buckling of the bellows, and a further shorter deformation stroke and excellent energy absorption efficiency can be realized.

  The neutral axis in the present invention refers to a line of intersection between the neutral surface and the side portion, and the neutral surface is a surface including the centroid in each cross section in the short direction, and includes compressive stress and It is a surface where none of the tensile stress acts. The centroid corresponds to the point of action when the resultant area is obtained by considering the size of the area of the figure as a force.

  According to the impact absorbing member of the present invention, when a bending load due to impact is applied, the bellows-like deformation promoting means provided on the side of the impact absorbing member buckles, so that the bending load is compressed in the longitudinal direction. As a result of avoiding the collapse of the cross section and preventing the bending load from being lowered, the bending energy absorption efficiency can be improved. Therefore, the impact absorbing member of the present invention can achieve both a shorter deformation stroke and superior energy absorption efficiency than conventional ones.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, about the same component, the same code | symbol is attached | subjected and the description is abbreviate | omitted or simplified.

  The perspective view of the impact-absorbing member 1 which is one Embodiment of this invention is shown in FIG. The shock absorbing member 1 includes a compression part 10 where a compressive stress is generated by directly receiving an impact, a tensile part 12 where a tensile stress is generated opposite to the compression part 10, and the compression part 10 and the tensile part 12. It has a pair of side part 14 which connects both ends. The side portion 14 is provided with a bellows-like deformation promoting means 16, and the bellows-like deformation promoting means 16 is a continuous connecting a plurality of peaks 162 and valleys 164 having the same radius of curvature. It has a shape. In addition, if the area | region where this deformation | transformation promotion means 16 is provided is the side part 14, it will not be specifically limited.

  Plan views of the shock absorbing member 1 are shown in FIGS. As shown in FIG. 2, the top of the valley 164 is disposed at a position on the inner side of the straight line m connecting both ends of the deformation promoting means 16 in the longitudinal direction. Further, as shown in FIG. 3, in the deformation promoting means 16, the curvature radius r1 of the peak 162 and the curvature radius r2 of the valley 164 are the same length. In this case, each peak 162 and valley 164 generates a stable and constant load during buckling. On the other hand, as shown in FIG. 4, as a modification of the present embodiment, shock absorbing means provided with a deformation promoting means in which the curvature radius r2 of the valley portion 164 ′ is larger than the curvature radius r1 of the peak portion 162 ′. Member. In this modification, the valley 164 ′ having a large curvature radius is more likely to buckle than the peak 162 ′, and a certain load is preferentially generated.

[Shock absorbing mechanism]
FIG. 5 is a diagram showing an impact absorbing mechanism in the impact absorbing member 1 of the present invention. In general, when the structural member is subjected to bending deformation due to an impact, compressive stress in the direction of the arrow is generated in the vicinity of the impact pressurizing portion 9 in the side portion 14, opposite to the impact pressurizing portion 9 in the side portion 14. A tensile stress in the direction opposite to the compressive stress is generated on the side. The reason why the structural member is bent is that the bending load of the structural member is reduced. The decrease in the bending load is caused by the impact pressure portion 9 and the side portion 14 buckling due to the compressive stress, and the cross section is crushed. It is because it ends. In the present invention, the deformation promoting means 16 provided in the side portion 14 uses this compressive stress to convert the bending load into a longitudinal compressive load, and avoids the collapse of the cross section, thereby reducing the bending load. It is possible to prevent the decrease, and as a result, the bending energy absorption efficiency can be improved.

[Shape of shock absorbing member]
The impact absorbing member 1 of the present invention has a longitudinal direction and a transverse direction, and absorbs the impact by being bent and deformed substantially perpendicular to the longitudinal direction at the time of impact. The shape of the shock absorbing member 1 according to the present invention is not particularly limited as long as it is a hollow shock absorbing member. For example, a cross-sectional polygonal shape such as a quadrangular prism and a cylindrical shape can be given, and the cross-sectional shape may differ depending on the location.

[Material of shock absorbing member and deformation promoting means]
The deformation promoting means 16 according to this embodiment is formed of a fiber reinforced plastic material. For example, carbon fiber, glass fiber, aramid fiber, basalt fiber and the like can be used as the reinforcing fiber, and epoxy resin, polypropylene, unsaturated polyester, vinyl ester and the like can be used as the base plastic.

  Among the fiber reinforced plastic materials, carbon fiber reinforced plastic (CFRP) using carbon fibers as a reinforcing material is a lightweight, high strength, high elastic modulus material, and therefore suitable for forming the deformation promoting means 16 according to the present embodiment. Used for. Specifically, a laminate of CFRP UD material, cloth material, or the like can be used. For example, what laminated | stacked by changing the fiber direction of the sheet-like UD materials laminated | stacked so that the fiber direction of the sheet | seats to laminate | stack may have a fixed angle can be used. In addition, one sheet-like UD material and another sheet-like UD material are laminated to have a fiber orientation angle of 45 degrees and −45 degrees (hereinafter referred to as CFRP UD material [45 / − 45]) and the like can be used. Here, the “fiber orientation angle” is an angle determined from the central axis extending in the longitudinal direction through the center of gravity of the impact absorbing member and the fiber direction. The “fiber direction” is the fiber direction determined by aligning the fibers in one direction when forming a fiber reinforcing material such as a UD material or a cloth material. Since the load characteristics of the impact absorbing structure using the fiber reinforcing material are affected by the fiber orientation angle, an impact absorbing member having high energy absorption efficiency can be provided by appropriately setting the fiber orientation angle. The number of laminations and the fiber orientation angle are not particularly limited.

  Moreover, a prepreg can be used for formation of the deformation | transformation promotion means 16 which concerns on this embodiment. For example, a prepreg formed of a unidirectional UD material in which a plurality of sheet-like UD materials are aligned with the fiber direction aligned in one direction can be used.

  The material other than the deformation promoting means 16 is not particularly limited, and examples thereof include fiber reinforced plastics such as fiber reinforced plastics and fiber reinforced metals, metals such as iron and aluminum, and single resins. Can do.

<Manufacturing method>
An example of the manufacturing method of the impact absorbing member 1 according to the present embodiment is shown in FIG. As shown in FIG. 6, the deformation promoting means 16 provided in the impact absorbing member 1 according to the present embodiment includes an upper mold 22 provided with a continuous shape composed of a plurality of crests and troughs having a predetermined radius of curvature in advance. It is obtained by inserting a prepreg 100 in which a fiber-reinforced plastic material is wound into a squeeze shape between the lower dies 24, and closing these dies 2 and performing internal pressure molding. Subsequently, the impact-absorbing member 1 is obtained by arranging the obtained deformation promoting means 16 in a side portion such as a hollow iron material or aluminum material. In this way, only the deformation promoting means 16 can be molded with a fiber reinforced plastic material, and other portions can be molded with metal or the like, and the impact absorbing member 1 can be molded only by internal pressure molding of the fiber reinforced plastic material. is there.

<Application>
Since the impact absorbing member of the present invention can realize a short deformation stroke and a large energy absorption efficiency, it can be used for a member that requires excellent impact energy absorption. As such a member, for example, a beam material used for an automobile side part such as a front pillar, a center pillar, and a rear pillar of an automobile can be cited. The automobile using the impact absorbing member of the present invention as a structural member is excellent in durability against bending load when an impact is applied to the vehicle body due to a rear-end collision or the like. Can contribute to protection.

  FIG. 7 is a diagram showing an example in which the impact absorbing member of the present invention is applied as a beam material for an automobile center pillar. The automobile center pillar is a portion shown in FIG. 7A, and a beam material as an internal structural material exists in the center pillar as shown in FIG. 7B. FIG. 7C is a cross-sectional view taken along the line YY of the beam material shown in FIG. Generally, the load at the time of a collision from the side of the automobile is received from the direction indicated by the arrow. For this reason, it is effective to use the surface receiving the arrow direction as a load receiving surface (compressed portion) and to provide deformation promoting means for the side portion.

  Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

<Example 1>
[Overall configuration of shock absorbing member]
A hollow impact absorbing member having bellows-like deformation promoting means as shown in FIG. 8 was prepared. The unit of the numerical value of the length in FIG. 8 is mm, and the impact absorbing member is a hollow member having a length of 600 mm in the longitudinal direction and a cross section of 50 mm × 50 mm. A bellows-like deformation promoting means is provided in a 90 mm region at the P portion at the substantially central portion in the longitudinal direction of the shock absorbing member. In addition, the arrow in FIG.

  The impact absorbing member was manufactured as follows. First, a UD material using an epoxy resin (# 112) as a matrix is laminated on a carbon fiber HTA manufactured by Toho Tenax Co., Ltd. so that the laminated structure is [0/90/0/90/0] s. A sushi-wound prepreg was made in a sushi-wound shape. Next, this spirally wound prepreg is inserted between an upper mold and a lower mold, which are provided with a continuous shape consisting of a plurality of crests and troughs having a curvature radius of 25 mm in advance, and these molds are closed and subjected to internal pressure molding. Thus, a deformation promoting means was obtained. And the impact-absorbing member was obtained by arrange | positioning this deformation | transformation promotion means in the side part of the hollow member shape | molded the whole surface by UD material [0/90] 10ply.

<Comparative Example 1>
Comparative Example 1 was obtained by molding the entire surface with UD material [0/90] 10 ply in the same manner as in Example 1 except that the hollow member was not provided with deformation promoting means.

<Evaluation>
The impact absorbing member obtained in Example 1 and Comparative Example 1 was subjected to a three-point bending load displacement test. As a tester, Shimadzu Autograph was used, and the test speed was 5 mm / min. The measurement was performed with a load cell installed on the presser.

  The stress-strain curve obtained as a result of the test is shown in FIG. As shown in FIG. 9, compared to the comparative example, the example showed less load (stress) reduction after the yield point (maximum load) and higher impact energy absorption efficiency.

It is a perspective view of the impact-absorbing member which concerns on one Embodiment. It is an enlarged view of the deformation | transformation promotion means of the impact-absorbing member which concerns on one Embodiment. It is an enlarged view of the deformation | transformation promotion means of the impact-absorbing member which concerns on one Embodiment. It is an enlarged view of the deformation | transformation promotion means of the impact-absorbing member which concerns on a modification. It is drawing for demonstrating an impact-absorbing mechanism. It is drawing for demonstrating the manufacturing method of the impact-absorbing member which concerns on one Embodiment. It is drawing which shows the example which applied the impact-absorbing member which concerns on this invention to the beam material of a motor vehicle center pillar. It is a side view of the impact-absorbing member of Example 1. It is a figure which shows the stress-strain curve in an Example and a comparative example. It is drawing for demonstrating the structural member of patent document 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 3 Shock-absorbing member 10, 10 'Compression part 12 Tensile part 13 Neutral shaft 14 Lateral part 16 Deformation promotion means 162, 162' Mountain part 164, 164 'Valley part 2 Type 22 Upper mold 24 Lower mold 30 Pillar material 100 Prepreg 300 Structural member 301 Load receiving surface 302 Folded part 303 Joint part

Claims (4)

A hollow impact absorbing member that has a longitudinal direction and a transverse direction and absorbs impact by bending deformation,
A compression site where compressive stress is generated by receiving the impact directly; a tensile site where tensile stress is generated opposite to the compression site; and a pair of side sites connecting both ends of the compression site and the tensile site; Have
At least the side portion is provided with bellows-like deformation promoting means composed of a plurality of peaks and valleys having a predetermined radius of curvature,
The said deformation | transformation promotion means is an impact-absorbing member arrange | positioned in the position which the top part of the said trough part becomes inside from the line | wire which connects the both ends of the said deformation | transformation promotion means in the said longitudinal direction.   The impact absorbing member according to claim 1, wherein the deformation promoting means is arranged in a direction in which each ridge line of the peak portion and the valley portion is substantially orthogonal to the longitudinal direction.   The impact absorbing member according to claim 1 or 2, wherein the radii of curvature of the ridges and valleys are different from each other.   The impact absorbing member according to any one of claims 1 to 3, wherein the deformation promoting means provided in the side part is disposed from the compression part side to the tension part side across a neutral axis.

Images