Shock absorption member

Abstract

To provide a shock absorption member capable of sufficiently exhibiting an effect by a reinforcement part.SOLUTION: A shock absorption member is deformed by receiving an impact load. The shock absorption member includes a body part and a reinforcement part. The body part and the reinforcement part extend in a load direction and are joined to each other so as to transmit a load. The reinforcement part is provided to separate from an impact load reception surface side top surface of the body part. When a Young's modulus and length in an impact load application direction of the body part are defined as E1 and L1, respectively and a Young's modulus and length in the impact load application direction of the reinforcement part are defined as E2 and L2, E1<E2 and L1>L2 are satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a shock-absorbing member improved to efficiently absorb shock energy by appropriately arranging different materials against an externally received shock.

Background Art

[0002] In transportation equipment such as automobiles or railway vehicles, shock-absorbing members that absorb shock energy and mitigate the shock during a collision are provided at the front, side, and / or rear of the vehicle. In such a vehicle shock-absorbing member, in order to suppress the shock to pedestrians and passengers and keep the load substantially constant (make the load-displacement diagram during a collision a rectangular wave) to ensure an efficient energy absorption amount, a shock-absorbing member that reinforces the main body with a reinforcing portion of a different material species from the main body may be adopted.

[0003] Among these, a shock-absorbing member (Patent Document 1) provided with a reinforcing portion on the outer shell layer that receives the shock, or a shock-absorbing member (Patent Document 2) provided with a reinforcing portion containing fibroin fibers in the base material so that the reinforcing portion receives the shock has been proposed. Also, a shock-absorbing member (Patent Document 3) has been proposed in which a reinforcing portion having a tensile strength higher than the compressive strength of the fiber-reinforced resin is sandwiched between the fiber-reinforced resins so that the reinforcing portion receives the shock.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in any of the prior art documents, since the reinforcing portion is arranged in a direction orthogonal to the direction in which the impact load acts, the extending direction of the impact load does not coincide with that of the reinforcing portion, so the reinforcing portion cannot support the impact load, and it cannot be said that a sufficient reinforcing effect has been obtained. For example, in Patent Document 1, in a situation where the impact load is relatively small, such as in baseball or softball assumed in Patent Document 1, a reinforcing portion is provided in the outer shell layer that receives the impact load, and a buffer material layer is arranged inside, so as to gradually reduce the impact load. However, under a large impact load such as a collision between vehicles, it is not uncommon for the hardest outer shell layer to be damaged. When the outer shell layer is damaged first, the overload applied to the inner buffer material and the impact load cannot be absorbed, and the impact absorbing member cannot exhibit the assumed effect. Alternatively, in Patent Document 2 or Patent Document 3, the reinforcing portion and the base material are arranged in the order with respect to the direction in which the impact load is applied, and it is assumed that the impact absorbing member absorbs the impact by bending deformation with respect to the impact load from the outside. However, when the impact absorbing member is crushed by the impact load like the impact absorbing member mounted on a vehicle to absorb the impact load, the reinforcing portion does not deform, and an overload occurs in the base material arranged on the downstream side in the impact load application direction, so that the reinforcing effect of the reinforcing portion cannot be sufficiently obtained.

[0006] Therefore, in view of the above problems, an object of the present invention is to provide an impact absorbing member capable of sufficiently exerting the effect of the reinforcing portion.

Means for Solving the Problems

[0007] In order to solve the above problems, an impact absorbing member according to the present invention is an impact absorbing member that deforms when receiving an impact load, the impact absorbing member includes a main body portion and a reinforcing portion, the main body portion and the reinforcing portion extend along the load direction and are joined so that the load is transmitted to each other, and the reinforcing portion is provided at a distance from the top surface on the impact load receiving surface side of the main body portion. When the Young's modulus of the main body portion is E1, the length in the impact load application direction is L1, the Young's modulus of the reinforcing portion is E2, and the length in the impact load application direction is L2, it is characterized in that E1 < E2 and L1 > L2.

[0008] Thus, in the shock-absorbing member according to the present invention, it is preferable that the end position of the reinforcing portion on the anti-shock load side in the shock load application direction coincides with the end position of the main body portion on the anti-shock load side.

[0009] Further, it is preferable that the reinforcing portion is arranged symmetrically with respect to the central axis of the main body portion.

[0010] Also, the Young's modulus E2 of the reinforcing portion is preferably 10 times or more and 200 times or less the Young's modulus E1 of the main body portion.

[0011] Also, the length L2 of the reinforcing portion in the shock load application direction is preferably 0.8 times or more and 0.95 times or less the length L1 of the main body portion in the shock load application direction.

[0012] Further, it is preferable that a part or the whole of the reinforcing portion is joined to the main body portion by adhesion, welding, or fastening.

[0013] Also, it is preferable that the main body portion is made of any of a thermoplastic resin, a thermosetting resin, or a fiber-reinforced resin composition containing a resin and reinforcing fibers.

[0014] Also, as the reinforcing portion, a metal material is preferable.

[0015] Furthermore, it is preferable that the shock-absorbing member is used for a vehicle.

Advantages of the Invention

[0016] According to the shock-absorbing member of the present invention, since both the main body portion and the reinforcing portion extend along the direction in which the shock load is received, it is possible to easily obtain a load characteristic in which the load is substantially constant as the entire shock-absorbing member, and it is possible to exhibit highly efficient shock energy absorption characteristics.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

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Figure 9

Best Mode for Carrying Out the Invention

[0018] Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a shock-absorbing member according to the first embodiment (Example 1) of the present invention. In FIG. 1, reference numeral 100 denotes the shock-absorbing member. Reinforcing portions 102 are provided at two positions symmetrically with respect to the main body portion 101 and the center 103 of the shock-absorbing member along the shock load application direction (the Z direction in the figure and the downward direction in the figure). Regarding the center 103 of the shock-absorbing member, it is preferable to adopt, for example, the center of gravity as the center so that the shock-absorbing member is maintained in mechanical stability. Alternatively, the center of the figure may be adopted with respect to the top surface 105 on the collision surface side of the main body portion 101. Further, the main body portion 101 and the reinforcing portion 102 are fastened by bolts 104 at six positions on one side (twelve positions in total). Note that the shock-absorbing member 100 is an example of the shock-absorbing member created in the present embodiment, and is not limited to the shape of the shock-absorbing member according to the present invention.

[0019] The impact absorbing member 100 extends along the load direction, and the reinforcing portion 102 is spaced apart from the top surface 105 on the collision surface side of the main body portion 101. When the length of the main body portion 101 in the impact load application direction is L1 and the length of the reinforcing portion 102 in the impact load application direction is L2, it is provided such that L1 > L2. The impact absorbing member 100 is preferable in that the main body portion 101 and the reinforcing portion 102 constituting the impact absorbing member 100 extend in the load direction, so that the impact load can be effectively supported. Alternatively, since the reinforcing portion 102 is provided spaced apart from the collision surface side of the main body portion 101, resulting in L1 > L2, the reinforcing portion 102 does not contribute to the first peak load that can be the maximum load in the load-displacement diagram. Therefore, it is preferable from the viewpoint that the maximum load can be kept the same whether the reinforcing portion 102 is provided or not. More preferably, the length L2 of the reinforcing portion in the impact load application direction, for which the effect was obtained in Example 1 described later, can be 0.95 times or less the length L1 of the main body portion in the impact load application direction. On the other hand, the lower limit of the length L2 of the reinforcing portion in the impact load application direction is preferably 0.8 times or more the length of the main body portion in the impact load application direction in order to obtain the reinforcing effect of the reinforcing portion.

[0020] Although the interior of the main body 101 provided in the shock absorption member 100 is not particularly limited, it may be solid, hollow, or ribs may be formed. Also, although the shape is not particularly limited, it may be a prism, a cylinder, or a polygonal column. Although the material of the main body is not particularly limited, from the viewpoint of light weight, it is preferably composed of any of a thermoplastic resin, a thermosetting resin, and a fiber-reinforced resin composition containing a resin and a reinforcing fiber. For example, as the thermoplastic resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polytrimethylene terephthalate resin, polyethylene naphthalate resin, polyester resin, polyethylene resin, polypropylene resin, polyolefin resin, polyoxymethylene resin, polyamide resin, polyphenylene sulfide resin, polyketone resin, polyether ketone resin, polyether ether ketone resin, polyether ketone ketone resin, polyether nitrile resin, fluorine-based resins such as polytetrafluoroethylene, liquid crystal polymer, styrene-based resin, polycarbonate resin, polymethyl methacrylate resin, polyvinyl chloride resin, polyphenylene ether resin, polyimide resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyether sulfone resin, polyarylate resin, phenoxy resin, copolymers and modified products thereof, and blends of two or more selected from such copolymers and modified products can be exemplified. Or, as the thermosetting resin, epoxy resin, unsaturated polyester resin, phenol resin, melamine resin, polyurethane resin, silicone resin, maleimide resin, vinyl ester resin, cyanate ester resin, and a resin obtained by prepolymerizing maleimide resin and cyanate ester resin can be exemplified. Alternatively, the fiber-reinforced resin composition containing a resin and a reinforcing fiber can be combined with the exemplified thermoplastic or thermosetting resin and a reinforcing fiber exemplified by glass fiber, carbon fiber, aramid fiber, polyethylene fiber, zylon fiber, boron fiber. From the viewpoint of obtaining the effect of the reinforcing fiber, it is preferable to blend 10% by weight or more and 80% by weight or less of the reinforcing fiber based on the fiber-reinforced resin composition as the blending ratio of the reinforcing fiber. A more preferable blending ratio of the reinforcing fiber is 20% by weight or more and 50% by weight or less.

[0021] The reinforcing part 102 provided in the shock absorption member 100 is arranged point-symmetrically and line-symmetrically with respect to the center of the shock absorption member 100 about the axis of the shock load application direction. The position of the reinforcing part 102 is not particularly limited, and it may be inside the main body part, outside the main body part, or on one surface or the entire surface outside the main body part, or may be inside the hollow main body part. Preferably, the reinforcing part 102 is preferably arranged symmetrically with respect to the central axis of the main body part 101 so that there is no difference in the second moment of area in the orthogonal directions (the x-axis and y-axis in the figure) about the axis of the shock load application direction. At this time, by adopting the center of gravity as the center, the entire shock absorption member 100 including the main body part 101 and the reinforcing part 102 is kept mechanically stable, which is preferable.

[0022] The main body part 101 and the reinforcing part 102 are fastened by bolts 104. It is preferable that a part or the entire surface of the reinforcing part 102 is joined to the main body part 101 by adhesion, welding, or fastening, so that the reinforcing part 102 can deform following the main body part 101 and the reinforcing effect can be maximally exerted. The joining method is not limited to bolt fastening, and examples include joining by adhesion, welding, or fastening represented by screws, rivets, and fitting.

[0023] In order to obtain the reinforcing effect on the main body part 101, when the Young's modulus of the main body part 101 is E1 and the Young's modulus of the reinforcing part 102 is E2, it is preferable to select the material so that E1 < E2. Alternatively, since it is important that the Young's modulus of the reinforcing part 102 is higher than that of the main body part 101, the main body part 101 and the reinforcing part 102 may be made of two different types of thermoplastic resins, thermosetting resins, or fiber-reinforced resins composed of resins and reinforcing fibers, with a material having a small Young's modulus as the main body part 101 and a material having a large Young's modulus as the reinforcing part 102. More preferably, the Young's modulus E2 of the reinforcing part 102 is set to be 10 times or more and 200 times or less the Young's modulus E1 of the main body part 101, so that the difference in Young's modulus between the main body part 101 and the reinforcing part 102 becomes significant and a sufficient reinforcing effect can be obtained. For example, since a metal material has excellent rigidity, it can be selected as the material of the reinforcing part 102.

[0024] Here, regarding the effects of the structure of the shock-absorbing member 100 according to the above-described Example 1, the effects will be explained based on the results of simulating a drop weight test by the finite element method (FEM). FIG. 3 shows a simulation model for performing the finite element method. Simulation software LS-DYNA (version 971 R10.2.0) manufactured by ANSYS, which is widely used in the academic and industrial fields, is used. However, analysis software and external programs that can consider the deformation of the shock-absorbing member due to impact may also be used.

[0025] In the simulation model, the dimensions of the shock-absorbing member 100 are such that the main body portion 101 is 60 mm × 60 mm × 100 mm (x direction × y direction × z direction). The main body portion 101 has a thickness of 2.25 mm on the surface receiving the impact and has a gradient of 0.5 degrees that flares out towards the anti-shock end of the shock-absorbing member 100. The reinforcing portion 102 has dimensions of 60 mm × 95 mm (y direction × z direction) and a thickness of 2 mm (x direction). FIG. 2 is a schematic front view showing a simulation model of the drop weight test of the shock-absorbing member 100 according to the first embodiment (Example 1). As shown in FIG. 2, with the shock-absorbing member 100 standing upright on the base portion 200, a predetermined weight 201 is dropped from above in the direction of the impact energy 202 to crush the shock-absorbing member 100 in the z direction of FIG. 2. Regarding the various conditions of this drop weight test, the weight of the weight was 225 kg and the drop height was 1 m, and the displacement from the start of the compressive deformation of the shock-absorbing member 100 and the load generated by such compressive deformation were output. As the resin used for the main body portion 101 of the shock-absorbing member 100, a fiber-reinforced resin (Young's modulus: 2.7 GPa, strength: 76 MPa) manufactured by Toray Industries, Inc. was used. Also, as the material used for the reinforcing portion 102, a general steel material (Young's modulus: 205 GPa, strength: 571 MPa) was used. FIG. 3 is a load-displacement diagram of Example 1 and Comparative Example 1, and 300 in FIG. 3 is the load-displacement diagram of Example 1.

[0026] FIG. 4 shows the shock-absorbing member of Comparative Example 1, where (a) is a schematic front view and (b) is a schematic front view showing the state of deformation in the simulation model of the drop weight test. Under the condition that the shock-absorbing member 400 (Comparative Example 1) composed only of the main body 101 shown in FIG. 4(a) was erected on the base 200, a simulation was performed under the same conditions of the drop weight test as in Example 1. As a result, a load-displacement diagram like 301 in FIG. 3 was obtained. Immediately after deformation, the load gradually increases, but the load of the shock-absorbing member 400 composed only of the main body 101 drops rapidly after the first peak load. FIG. 2(b) shows the deformation behavior of the shock-absorbing member 100 immediately after the first peak load, and FIG. 4(b) shows the deformation behavior of the shock-absorbing member 400 immediately after the first peak load. It was confirmed that both the shock-absorbing member 100 and the shock-absorbing member 400 deformed while the main body 100 was crushed. Also, in the shock-absorbing member 100, it was confirmed that the reinforcing portion 101 was deformed. On the other hand, with respect to the load-displacement diagram 300 of the shock-absorbing member 100, it was confirmed that the load-displacement diagram 301 of the shock-absorbing member 400 showed a rapid drop in load immediately after the first peak load. This is considered to be because in the shock-absorbing member 400, only the main body 101 supports the impact load of the weight 201, so the load dropped rapidly with the crushing of the main body 101. On the other hand, in the shock-absorbing member 100 having the reinforcing portion 102, it is considered that the rapid drop in load generated in the shock-absorbing member 400 could be avoided because the reinforcing portion 102 supports the load even when the main body 101 is crushed by the impact load of the weight 201.

[0027] FIG. 5 shows the shock-absorbing member of Comparative Example 2, where (a) is a schematic front view and (b) is a schematic front view showing the state of deformation in the simulation model of the drop hammer test. A shock-absorbing member 500 (Comparative Example 2) having a reinforcing portion 501 with the same length as the main body portion 101 in the impact load application direction as the main body portion 101 shown in FIG. 5(a) was erected on the base portion 200, and a simulation was performed under the same conditions of the drop hammer test as in Example 1. FIG. 6 is the load-displacement diagram of Comparative Example 2, and 600 in FIG. 6 is the load-displacement diagram of Comparative Example 2. Immediately after deformation, the load exceeded the first peak load generated in the shock-absorbing member 100, and thereafter the transition of the load was the same as that of the load-displacement diagram 300 of the shock-absorbing member 100. The load-displacement diagram 600 of the shock-absorbing member 500 has the first peak load greatly exceeding the overall load value, and it is difficult to say that the load transition is substantially constant. FIG. 5(b) shows the deformation behavior of the shock-absorbing member 500 immediately after the first peak load. At the first peak load, both the main body portion 101 and the reinforcing portion 501 are deformed greatly at the same time. It is considered that, in addition to the main body portion 101, the deformation resistance of the reinforcing portion 501 is added to the load-displacement diagram, resulting in a large increase in the first peak load. Therefore, in order to keep the load substantially constant, it is necessary to provide the reinforcing portion spaced apart from the collision surface side of the main body portion.

[0028] FIG. 7 shows the shock-absorbing member of Comparative Example 3, where (a) is a schematic front view and (b) is a schematic front view showing the state of deformation in the simulation model of the drop hammer test. A simulation was performed under the same conditions of the drop hammer test as in Example 1, with the shock-absorbing member 700 (Comparative Example 3) having the reinforcing portion 701 provided on the top surface of the main body portion 101 shown in FIG. 7(a) standing on the base portion 200. FIG. 8 is the load-displacement diagram of Comparative Example 3, and 800 in FIG. 8 is the load-displacement diagram of Comparative Example 3. Immediately after deformation, the load gradually increases, but crushing occurs in the main body portion 101, and it is considered that the load drops suddenly in the same manner as the load-displacement diagram 301 of the shock-absorbing member 400. This is because the reinforcing portion 701 does not extend in the direction of the impact load, so the impact load is transmitted directly to the main body portion 101 without the reinforcing portion 701, which is more rigid than the main body portion against the impact load, being deformed, and only the main body portion 101 is deformed. Therefore, since the deformation of the main body portion 101 absorbed the impact load, the load-displacement diagram of Comparative Example 3 was almost the same as the load-displacement diagram 301 of Comparative Example 1, and the reinforcing effect of the reinforcing portion was not manifested. Therefore, the shock-absorbing member 100 in which the main body portion 101 and the reinforcing portion 102 extend in the load direction as in Example 1 is preferably used as a structure that can most effectively obtain the reinforcing effect of the reinforcing portion.

[0029] The structure of the shock-absorbing member according to the present invention is not limited to that shown in FIG. 1, and various structures can be adopted as long as the requirements defined in the present invention are satisfied. FIG. 9 shows a perspective view showing various structural examples of the shock-absorbing member according to the present invention. For example, as shown in FIG. 9(a), a shock-absorbing member 900 in which a reinforcing portion 902 is provided on one surface of the outer surface of a main body portion 901 configured in a lattice shape, as shown in FIG. 9(b), a shock-absorbing member 1000 in which reinforcing portions 1002 are provided on two surfaces of the outer surface of a main body portion 1001 configured in a lattice shape, as shown in FIG. 9(c), a shock-absorbing member 1100 in which a reinforcing portion 1102 is provided inside a main body portion 1101 configured in a box-shaped cavity so as to be joined to at least a part of the inner surface of the main body portion 1101, as shown in FIG. 9(d), a shock-absorbing member 1200 in which a reinforcing portion 1202 is provided in a part of the inside of a main body portion 1201 configured in a lattice shape, as shown in FIG. 9(e), a shock-absorbing member 1300 in which a reinforcing portion 1302 is provided on one surface of the outer surface of a main body portion 1301 configured in a honeycomb shape, as shown in FIG. 9(f), a shock-absorbing member 1400 in which reinforcing portions 1402 are provided on two or three surfaces of the outer surface of a main body portion 1401 configured in a honeycomb shape, as shown in FIG. 9(g), a shock-absorbing member 1500 in which a reinforcing portion 1502 is provided inside a main body portion 1501 configured in a honeycomb shape, as shown in FIG. 9(h), a shock-absorbing member 1600 in which a reinforcing portion 1602 is provided in a part of the inside of a main body portion 1601 configured in a honeycomb shape with ribs, as shown in FIG. 9(i), a shock-absorbing member 1700 in which reinforcing portions 1702 are provided at at least two locations (preferably, point-symmetrically or line-symmetrically) inside a main body portion 1701 configured in a honeycomb shape with ribs, as shown in FIG. 9(j), a shock-absorbing member 1800 in which a reinforcing portion 1802 is provided outside a main body portion 1801 configured in a cylindrical shape, as shown in FIG. 9(k), a shock-absorbing member 1900 in which a reinforcing portion 1902 is provided inside a main body portion 1901 configured in a cylindrical shape, etc. can be exemplified.

Industrial Applicability

[0030] The shock-absorbing member of the present invention can be applied to any use where shock absorption is desired, particularly to any part of a vehicle, and in particular, in addition to the front part of an automobile body, it can be suitably applied to the rear part and side parts.

Description of Symbols

[0031] 100 Impact-absorbing member according to Example 1 101 Main body part 102 Reinforcing part 103 Center of the impact-absorbing member 104 Bolt for fastening the main body part and the reinforcing part 105 Top surface of the main body part 200 Base part used in the simulation of the drop hammer test 201 Hammer used in the simulation of the drop hammer test 202 Impact direction of the hammer 300 Load-displacement diagram of Example 1 301 Load-displacement diagram of Comparative Example 1 400 Impact-absorbing member of Comparative Example 1 500 Impact-absorbing member of Comparative Example 2 501 Reinforcing part provided in Comparative Example 2 600 Load-displacement diagram of Comparative Example 2 700 Impact-absorbing member of Comparative Example 3 701 Reinforcing part provided in Comparative Example 3 800 Load-displacement diagram of Comparative Example 3 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900 Impact-absorbing members 901, 1001, 1101, 1201, 1301, 1401, 1501, 1601, 1701, 1801, 1901 Main body parts 902, 1002, 1102, 1202, 1302, 1402, 1502, 1602, 1702, 1802, 1902 Reinforcing parts

Claims

1. An impact-absorbing member that deforms upon receiving an impact load, the impact-absorbing member comprising a main body portion and a reinforcing portion, the main body portion and the reinforcing portion extending along the load direction and being joined so that the load is transmitted between them, the reinforcing portion being provided spaced apart from the top surface on the impact load receiving surface side of the main body portion, when the Young's modulus of the main body portion is E1, the length in the impact load application direction is L1, the Young's modulus of the reinforcing portion is E2, and the length in the impact load application direction is L2, an impact-absorbing member characterized in that E1 < E2 and L1 > L2.

2. The impact-absorbing member according to claim 1, wherein an end position on the anti-impact load side of the reinforcing portion in the impact load application direction coincides with an end position on the anti-impact load side of the main body portion.

3. The impact-absorbing member according to claim 1, wherein the reinforcing portion is arranged symmetrically with respect to the central axis of the main body portion.

4. The impact-absorbing member according to claim 1, wherein the Young's modulus E2 of the reinforcing portion satisfies (10 × E1) ≤ E2 ≤ (200 × E1) with respect to the Young's modulus E1 of the main body portion.

5. The impact-absorbing member according to claim 1, wherein the length L2 of the reinforcing portion in the impact load application direction satisfies (0.8 × L1) ≤ L2 ≤ (0.95 × L1) with respect to the length L1 of the main body portion in the impact load application direction.

6. The impact-absorbing member according to claim 1, wherein part or all of the reinforcing portion is joined to the main body portion by adhesion, welding, or fastening.

7. The impact-absorbing member according to claim 1, wherein the main body portion is made of any one of a thermoplastic resin, a thermosetting resin, and a fiber-reinforced resin composition containing a resin and reinforcing fibers.

8. The impact-absorbing member according to claim 1, wherein the reinforcing portion is a metal material.

9. The impact-absorbing member according to any one of claims 1 to 8, wherein the impact-absorbing member is used for a vehicle.

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