Shock absorbing structure

Abstract

To provide a shock absorbing structure that can readily join a shock absorbing member to a tip member that is a separate member and has high shock absorption property.SOLUTION: A shock absorbing structure for absorbing impact energy includes a cylindrical shock absorbing member and a tip member. The cylindrical shock absorbing member includes an inside flange in one end. The cylindrical shock absorbing member is joined to the tip member via the inside flange.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a shock absorbing structure. [Background technology]

[0002] Many vehicles, such as automobiles, have shock absorbing structures at their front and rear to absorb impacts in collision accidents. A shock absorbing structure is comprised of a reinforcing member disposed between an exterior member of the vehicle, such as a bumper, and the vehicle body, and extending along the exterior member, and a shock absorbing member provided between the reinforcing member and the vehicle body. Patent Documents 1 and 2, for example, disclose examples of such shock absorbing structures, such as vehicle energy absorbing members that can be connected to bumper reinforcement and achieve stable energy absorption characteristics. Patent Document 3 discloses a shock absorbing structure that connects a shock absorbing member to a tip member and a base member, and that includes highly ductile connecting members. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-196463 [Patent Document 2] Japanese Patent Publication No. 2020-169002 [Patent Document 3] WO2023 / 120416 issue Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the energy absorption structure described in Patent Document 1, when connecting the impact absorbing portion to the bumper reinforcement, the energy absorber maintains a vertical overlap with the bumper reinforcement over its entire vertical height. Similarly, in Patent Document 2, when connecting the energy absorbing member to the bumper reinforcement, an attachment portion is used that connects to the upper wall of the bumper reinforcement. Therefore, in the energy absorption structures described in Patent Documents 1 and 2, if the overlapping portion shatters and scatters upon impact, there is a risk of damaging other components inside the vehicle. Furthermore, there is a risk that the attachment portion will not efficiently transmit energy to the impact absorbing portion, preventing the impact absorbing portion from collapsing properly. Furthermore, in both Patent Documents 1 and 2, separate parts are required to connect the bumper reinforcement and the impact absorbing member, resulting in multiple manufacturing processes. Furthermore, even if an attachment portion were to be integrally molded, an undercut would be created in the impact absorbing member, making the manufacturing process overly complicated.

[0005] In the first place, Patent Document 3 does not mention a method of attaching the device to a bumper reinforcement, and does not give detailed consideration to a method of connecting the device to the bumper reinforcement.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a shock absorbing structure that has high shock absorbing properties and in which a shock absorbing member can be easily joined to a tip member that is a separate part. [Means for solving the problem]

[0007] As a result of extensive investigations, the present inventors have found that the above problems can be solved by the following means, and have arrived at the present invention.

[0008] 1. A shock absorbing structure that absorbs impact energy, The shock absorbing structure includes a cylindrical shock absorbing member and a tip member, The cylindrical impact absorbing member has an inside flange at one end thereof, The cylindrical impact absorbing member and the tip member are joined via the inside flange. Impact absorbing structure. 2. The shock absorbing structure described in 1 above, wherein the end face at one end of the cylindrical shock absorbing member is an open surface with at least a portion open, and the inside flange extends toward the inside of the end face. 3. The shock absorbing structure according to 2, wherein the inside flange extends along the end face. 4. The shock absorbing structure includes a base member; An outside flange is provided at the other end of the cylindrical impact absorbing member, 4. The shock absorbing structure according to any one of 1 to 3, wherein the cylindrical shock absorbing member and a base end member are joined via the outside flange. 5. The impact absorbing member contains reinforcing fibers with a weight average fiber length of 1 mm or more and 100 mm or less and a resin, the orientation Tc of the reinforcing fibers contained in the cylindrical portion of the impact absorbing member; The orientation of the reinforcing fibers contained in the inside flange is set to Ti, 5. The shock absorbing structure according to any one of 1 to 4 above, wherein when the orientation of the reinforcing fibers in the outside flange is To, the following is satisfied: Tc < Ti Tc < To 6. The shock absorbing structure according to any one of 1 to 6 above, the impact absorbing member is a joined body of a first member having an open cross-sectional shape and a first side flange portion, and a second member having an open cross-sectional shape and a second side flange portion, The shock absorbing structure, wherein the first member and / or the second member is a reinforced fiber resin molding and is an integrally molded body having the inside flange. 7. The shock absorbing structure according to 6 above, The shock absorbing structure, wherein the first member and / or the second member is an integrally molded body having the outside flange. 8. An impact absorbing structure described in any one of 1 to 7, wherein the first member and / or the second member are arranged in order of increasing compressive strength from the front end side that receives the impact to the rear end side. 9. The impact absorbing member has a hollow structure consisting of an outer cylindrical portion and a hollow portion, 9. The shock absorbing structure according to any one of 1 to 8, wherein the inside flange remains inside the hollow portion during a collision. 10. The shock absorbing structure according to any one of 1 to 9 above, wherein the inside flange has a uniform thickness. 11. The shock absorbing structure according to any one of 1 to 10 above, The shock absorbing structure is mounted on the vehicle, the tip member is disposed between an exterior body of a vehicle frame and the vehicle frame, The base end member is a vehicle frame member. Impact absorbing structure. 12. A method for manufacturing the shock absorbing structure according to 6 above, The first member and the second member are integrally molded bodies manufactured by press molding a composite material containing reinforcing fibers and a resin using a first mold and a second mold, respectively. A method for manufacturing a shock absorbing structure. 13. The method for manufacturing a shock absorbing structure according to claim 12, wherein the cylindrical shock absorbing member and the base end member are joined via the outside flange. 14. A method for manufacturing the shock absorbing structure according to claim 13, The first member and / or the second member do not have an undercut portion. A method for manufacturing a shock absorbing structure. [Effects of the Invention]

[0009] According to the shock absorbing structure of the present invention, when an impact is received, the impact is not hindered by the inside flange much and is immediately transmitted to the shock absorbing member, so that the shock absorbing portion collapses sufficiently to absorb the impact. In other words, the tube of the shock absorbing portion can bloom and break.

[0010] In addition, the first member and / or the second member, which are components of the impact absorbing portion of the present invention, extend in opposite directions to the inside and outside of the inside flange and the outside flange, respectively. After molding is complete, the inside flange is not dragged by the mold when the mold is separated. Furthermore, undercut shapes can be easily avoided, improving manufacturing efficiency during press molding. [Brief explanation of the drawings]

[0011] [Figure 1] 1A is a perspective view schematically illustrating the general configuration of a shock absorbing structure 100 according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view of the shock absorbing structure 100 according to one embodiment of the present invention. [Figure 2] 1A, 1B, and 1C are perspective views schematically illustrating the shock absorbing part of the present invention. [Figure 3] An impact absorbing member that has no open surface and has a closed end surface at one end. [Figure 4] (A) A perspective view showing a schematic view of the shock absorbing part of the present invention. (B) A cross section taken along the X plane of Fig. 4(A). (C) A schematic view showing the molding of the first member (or the second member). The first member (or the second member) is integrally molded and has flanges that become inside flanges and outside flanges when the shock absorbing member is formed. [Figure 5] (A) A first member (or second member) having flanges at both one end and the other end that will become outside flanges when formed into an impact absorbing member. (B) A schematic diagram of the molding of the first member (or second member) of Figure 5(A). [Figure 6] 1 is a schematic diagram showing a first member having an open cross-sectional shape with a first side flange portion and a second member having an open cross-sectional shape with a second side flange portion; FIG. [Figure 7] 1 is a schematic diagram showing a cross-sectional shape of a shock absorbing member, which has a hollow structure consisting of an outer cylindrical portion and a hollow portion. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Shock absorbing structure] Fig. 1(A) is a perspective view showing a schematic configuration of a shock absorbing structure 100 according to one embodiment of the present invention. Fig. 1(B) is a cross-sectional view of the shock absorbing structure 100. The shock absorbing structure includes cylindrical shock absorbing members 20L and 20R and a tip member 10.

[0013] In the following description, the three orthogonal directions in the shock absorption structure 100 will be referred to in descending order of length as the left-right direction, the front-rear direction, and the up-down direction. For convenience, the following description will define the front, rear, left, right, up, and down directions, and will refer to the front as Fr, the rear as Rr, the left as L, the right as R, the up as U, and the down as D.

[0014] [Shapes of shock absorbing members 20L, 20R, and 201] 1. Cylindrical The shock absorbing members 20L, 20R, and 201 are cylindrical, as shown in FIG. 2A, and have an internal cavity. The Fr axis direction in FIGS. 1A, 1B, and 2B indicates the shock absorbing direction (axial direction of the outer cylindrical portion) of the shock absorbing members 20L, 20R, and 201. A cross section cut perpendicular to the shock absorbing direction (Fr direction) preferably has a closed cross-sectional shape. The cross-sectional shape is not particularly limited and may be circular, elliptical, polygonal, or other shapes, or may be a combination of circular, elliptical, and polygonal shapes. Other shapes include, for example, two M-shaped shapes as shown in FIGS. 2A and 2C. The cross-sectional area does not need to be constant; it may increase from one end to the other, or it may increase from one end to the other and then decrease again.

[0015] 2. One end and the other end The shock absorbing members 20L, 20R, and 201 have one end portion. The one end portion is the end portion where the shock absorbing members 20L, 20R, and 201 are first subjected to an impact, and is the end portion in the Fr direction in FIGS. 1(A) and 1(B) and 2(B). On the other hand, the other end is the end of the impact absorbing members 20L, 20R, 201 opposite to the one end, for example, the end in the Rr direction in FIGS. 1(A)(B) and 2(B).

[0016] 3.Hollow structure The impact absorbing members 20L, 20R, and 201 preferably have a hollow structure consisting of an outer cylindrical portion and a hollow portion. The hollow portion refers to the space inside the outer cylindrical portion. The outer cylindrical portion may have protrusions or ribs. Figure 7 shows an example of an outer cylindrical portion 701 and a hollow portion 702.

[0017] 4. Opening surface It is preferable that the end face at one end of the cylindrical impact absorbing members 20L, 20R, 201 is an opening surface that is at least partially open. The opening surface is exemplified by 203 in Fig. 2. The impact absorbing members 20L, 20R, 201 preferably have a hollow structure consisting of an outer cylindrical portion and a hollow portion, and the opening surface serves as an entrance / exit for accessing the hollow portion.

[0018] 5. Inside flange 202 The impact absorbing members 20L, 20R, 201 have an inside flange 202 (for example, 202 in FIG. 2(A)) at one end. The one end is the part that becomes the end of the impact absorbing members 20L, 20R, 201, and is also the part that connects to the tip member 10. The inside flange 202 refers to a flange that protrudes from the inside surface of the cylindrical impact absorbing members 20L, 20R, 201, and is exemplified by 202 in FIG. 2, for example.

[0019] 5.1 Role of inside flange 202 The cylindrical impact absorbing members 20L, 20R, 201 of the present invention and the tip member 10 are joined via the inside flange 202. There are no particular limitations on the joining method, and examples include fastening with bolts and nuts, welding, adhesion with an adhesive, joining with clips or clamps, joining with rings or pins, rivet joining, and riveting in which parts are joined using a combination of rivets and adhesive. In other words, the role of the inside flange 202 is to join the impact absorbing members 20L, 20R, 201 and the tip member 10.

[0020] 5.2 The inside flange 202 preferably extends along an end face 204 at one end. The end face at one end is, for example, the face indicated by 204 in FIG. 2(B), and can also be said to be the face at the end in the impact input direction. By providing the inside flange 202 so that it extends along the end face at one end, joining to the tip member 10 becomes easy. In other words, it is preferable from the viewpoint of ease of joining to design the end face shape of the inside flange 202 in accordance with the shape of the tip member 10.

[0021] 5.3 Inside flange 202 during collision Furthermore, it is preferable that the impact absorbing members 20L, 20R, and 201 have a hollow structure consisting of an outer cylindrical portion and a hollow portion, and that the inside flange 202 remain inside the hollow portion during a collision. The inside flange 202 serves to connect the impact absorbing members 20L, 20R, and 201 to the tip member 10. However, during a collision, the connection between the inside flange 202 and one end is immediately destroyed, and the inside flange 202 portion breaks into pieces. In this case, because the inside flange 202 of the present invention extends inward from the end face of one end, the broken pieces of the inside flange 202 remain connected to the bumper beam and, as a result, remain inside the hollow portion. This reduces the risk of damaging other components, even if they are located outside the cylindrical impact absorbing members 20L, 20R, and 201, when the impact absorbing structure of the present invention is installed in an automobile.

[0022] 5.4 When an inside flange is designed as an outside flange On the other hand, if the flange at one end is designed as an outside flange rather than an inside flange 202, when the outside flange breaks and breaks into fragments during a collision, they will fly outside the cylindrical impact absorbing member. For example, if the impact absorbing structure of the present invention is installed in an automobile, other components may be present outside the cylindrical impact absorbing member, damaging them. This is particularly problematic when the impact absorbing member contains reinforcing fibers with a weight-average fiber length of 1 mm to 100 mm and a resin. This is because, when the impact absorbing member of the present invention is a fiber-reinforced resin molding, it is preferable that it breaks into fragments while opening like petals upon breakage. If the impact absorbing member is a fiber-reinforced resin molding rather than a metal molding and the flange at one end is designed as an outside flange rather than an inside flange, the outside flange or a portion thereof will break into fragments and fly off during a collision.

[0023] 6. Outside flange 40L, 40R The shock absorbing structure preferably includes a base end member, and outside flanges 40L, 40R are provided at the other end of the cylindrical shock absorbing members 20L, 20R, 201, and the cylindrical shock absorbing members 20L, 20R, 201 are joined to the base end members 30L, 30R via the outside flanges 40L, 40R. In the present invention, the outside flanges 40L, 40R are preferably provided at the other end of the shock absorbing members 20L, 20R, 201, not at one end. The outside flanges 40L, 40R are exemplified by 205 in FIG. 2(C), for example.

[0024] [Impact absorbing structures as automotive parts] The shock absorbing structure is preferably for absorbing impact energy input to a bumper of an automobile. Hereinafter, a shock absorbing structure for absorbing impact energy input to a bumper of an automobile will be described.

[0025] The tip member 10 in the present invention is preferably a front bumper or a rear bumper of an automobile, and the impact absorbing members 20L, 20R, 201 are preferably joined to the front bumper or the rear bumper of the automobile via an inside flange 202.

[0026] The base end members 30L, 30R joined to the impact absorbing members 20L, 20R, 201 via the outside flanges 40L, 40R may be vehicle frame members. In other words, the impact absorbing members 20L, 20R, 201 may be joined directly to the vehicle frame members, and in this case, the base end members 30L, 30R, which are vehicle frame members, may be side members of the automobile.

[0027] In another embodiment, the shock absorbing structure is mounted on a vehicle, the tip member 10 is arranged between the exterior body of the vehicle frame and the vehicle frame, and the base end members 30L, 30R are arranged between the shock absorbing members 20L, 20R, 201 and the vehicle frame.

[0028] The front-rear direction of the shock absorbing structure coincides with the length direction of the vehicle, the left-right direction of the shock absorbing structure coincides with the width direction of the vehicle, and the up-down direction of the shock absorbing structure coincides with the height direction of the vehicle.

[0029] The shock absorbing structure preferably includes shock absorbing members 20R and 20L arranged spaced apart in the left-right direction (Fig. 1). The shock absorbing members 20R and 20L are members that absorb, by deformation, the impact energy input to the tip member 10 described below. The shock absorbing members 20R and 20L preferably have the same structure, and are arranged symmetrically with respect to a line of symmetry that extends in the front-rear direction and is set at the center position of the shock absorbing structure in the left-right direction.

[0030] The shock absorbing members 20R and 20L are each a cylindrical structure with its axial direction extending in the front-to-rear direction (FIG. 1(A)). The shock absorbing members 20R and 20L are preferably made of a composite material containing reinforcing fibers and resin, and various shapes and materials such as those described in U.S. Patent Application Publication No. 20150356334 or WO 2020 / 129227 can be used. When the shock absorbing members 20R and 20L are made of a composite material, the tensile elongation of each of the shock absorbing members 20R and 20L is preferably less than 5%.

[0031] The shock absorbing structure preferably further includes a plate-shaped base end member 30R joined to the rear end surface of the shock absorbing member 20R, and a plate-shaped base end member 30L joined to the rear end surface of the shock absorbing member 20L. The base end members 30R and 30L are arranged such that their thickness directions coincide with the front-rear direction. The base end members 30R and 30L may each be made of a metal such as aluminum, but are not limited to this.

[0032] The shock absorbing structure may further include a cylindrical tip member 10 that extends in the left-right direction while curving forward from near the front end of the shock absorbing member 20R to near the front end of the shock absorbing member 20L. The tip member 10 (for example, 10 depicted in FIG. 1) is preferably a bumper reinforcement and is made of a metal such as aluminum, but is not limited to this. The tip member 10 has a shape that is symmetrical with respect to a line of symmetry that extends in the front-rear direction and is set at the center position of the shock absorbing structure in the left-right direction.

[0033] The tip member 10 (10 in FIG. 1) preferably comprises a plate-shaped upper surface portion (10U in FIG. 1) whose thickness direction coincides with the vertical direction, a plate-shaped lower surface portion (10D) arranged below the upper surface portion (10U in FIG. 1) and whose thickness direction coincides with the vertical direction, a curved plate-shaped front surface portion (10Fr in FIG. 1) connecting the front end edge of the upper surface portion (10U in FIG. 1) and the front end edge of the lower surface portion (10D), and a curved plate-shaped rear surface portion (10Rr) connecting the portion of the rear end edge of the upper surface portion (10U in FIG. 1) excluding both end portions and the portion of the rear end edge of the lower surface portion (10D in FIG. 1) excluding both end portions.

[0034] [Fiber orientation of impact absorbing members 20L, 20R, and 201] 1. Random distribution The state of the reinforcing fibers in the composite material is not particularly limited, and may be, for example, arranged in one direction or randomly. From the viewpoint of uniformity of the shape rigidity and strength of the impact absorbing members 20L, 20R, 201, it is preferable that the reinforcing fibers be in a two-dimensional random dispersion state in which the long axis directions of the reinforcing fibers are randomly dispersed in the in-plane direction of the composite material.

[0035] 2. Fiber orientation measurement method The degree of orientation of the two-dimensionally randomly dispersed reinforcing fibers is evaluated by calculating the ratio of the tensile modulus in two mutually perpendicular directions. The reinforcing fibers can be evaluated as being two-dimensionally randomly dispersed if the ratio (Eδ) obtained by dividing the larger of the tensile modulus values ​​measured in any direction of the impact absorbing members 20L, 20R, and 201 by the smaller of the two measured tensile modulus values ​​in the direction perpendicular to that direction is 5 or less, more preferably 2 or less, and even more preferably 1.5 or less. Because the impact absorbing members 20L, 20R, and 201 are cylindrical and curved, the two-dimensional random dispersion in the in-plane direction can be evaluated by making slits in the impact absorbing members 20L, 20R, and 201, heating them above their softening temperature, and solidifying them to return them to a flat plate shape. Then, test specimens can be cut out and the tensile modulus measured to confirm the state of random dispersion in the two-dimensional direction. More specifically, since the impact absorbing members 20L, 20R, and 201 of the present invention are a joined body of a first member having an open cross-sectional shape with a first side flange portion and a second member having an open cross-sectional shape with a second side flange portion, it is advisable to cut out a sample from the first member and / or the second member for evaluation.

[0036] 3. Orientation of reinforcing fibers in inside flange and outside flange The impact absorbing members 20L, 20R, and 201 of the present invention contain reinforcing fibers having a weight average fiber length of 1 mm or more and 100 mm or less, and a resin, the orientation Tc of the reinforcing fibers contained in the cylindrical portions of the impact absorbing members 20L, 20R, 201; The orientation of the reinforcing fibers contained in the inside flange 202 is set to Ti, When the orientation of the reinforcing fibers in the outside flanges 40L, 40R is To, it is preferable that the following is satisfied. Tc < Ti Tc < To

[0037] This design allows the cylindrical portion to be molded without causing the composite material to flow, while the inside and outside flange portions can be molded by flow molding, making it easy to mold them into a single piece. Note that the fiber orientation in the non-flow region tends to maintain the fiber orientation of the composite material, while in the flow region, the fiber orientation of the composite material is less likely to be maintained.

[0038] Figure 4(B) shows an area 402 that becomes the inside flange 202 when the shock absorbing members 20L, 20R, and 201 are formed, an area 403 that becomes the outside flanges 40L and 40R when the shock absorbing members 20L, 20R, and 201 are formed, and an area 404 that becomes the cylindrical portion when the shock absorbing members 20L, 20R, and 201 are formed.

[0039] [First and second members] The impact absorbing members 20L, 20R, 201 are preferably a joined body of a first member having an open cross section and a first side flange portion, and a second member having an open cross section and a second side flange portion.

[0040] When the first member and the second member are joined via the first side flange portion and the second side flange portion, the shock absorbing member 20L, 20R, 201 has a closed cross-sectional shape. The cross section of the first member and / or the second member as viewed from the shock absorbing direction (as viewed from the Fr direction) may be hat-shaped. Figure 6 shows an example of the cross section of the first member and the second member as viewed from the Fr direction. When the first side flange portion 601 and the second side flange portion 602 are joined, the shock absorbing member 201 has a closed cross-sectional shape.

[0041] The method for joining the first member and the second member is not particularly limited, and examples thereof include fastening with bolts and nuts, welding, adhesion with an adhesive, joining with clips or clamps, joining with rings or pins, press-fit joining, rivet joining, rivet bonding in which parts are joined by a combination of rivets and an adhesive, etc. When the first member and the second member are fiber-reinforced resin molded bodies and the resin contained therein is a thermoplastic resin, they are preferably joined by welding, and more preferably joined by vibration welding.

[0042] [First member and / or second member: integrally molded body] The first member and / or the second member is preferably a fiber-reinforced resin molded body, and is an integrally molded body having an inside flange 202. The inside flange 202 may be provided by being integrally molded into at least one of the first member and the second member, but is preferably provided by being integrally molded into both the first member and the second member. If the same molding die is used to manufacture the first member and the second member, both members will have the same shape. If they have the same shape, the molding die can be shared, and inventory management will be easier.

[0043] It is more preferable that the first member and / or the second member be an integrally molded body having outside flanges 40L, 40R.

[0044] Integral molding refers to the fact that these components are molded continuously without any seams and are not formed by joining separate components. Such integral molding allows the structure to be created in a single molding operation, preferably by press molding. Because the impact absorbing members 20L, 20R, and 201 are created by integral molding, separate components can be processed into a single component, lowering the unit price of the component. Furthermore, the number of assembly steps is reduced, and the reduced number of components also reduces inventory costs. When the impact absorbing members 20L, 20R, and 201 are created by integral molding, the inside flange 202 and the outside flanges 40L and 40R preferably contain reinforcing fibers with a weight-average fiber length of 1 mm or more and 100 mm or less and a thermoplastic resin, and the reinforcing fibers preferably exist transversely from the outer tubular portion to the inside flange 202 and the outside flanges 40L and 40R.

[0045] [Uneven thickness structure] The first and / or second members are preferably arranged in order of increasing compressive strength from the leading end side to the rear end side where the impact is received. By making the thickness of the first and / or second members uneven so that they increase from the leading end side to the rear end side where the impact is received, the first and / or second members can be arranged in order of increasing compressive strength from the leading end side to the rear end side.

[0046] By using such a first member and / or second member, the shock absorption members 20L, 20R, and 201 are arranged in order of increasing compressive strength from one end to the other end. In other words, from one end to the other end of the shock absorption members 20L, 20R, and 201, a thickness non-uniform structure is formed such that the thickness increases.

[0047] In this case, since destruction occurs in order from one end (the shock input side) to the other end, the entire shock absorption part can be utilized to absorb the shock. When the thickness is constant, it is difficult to determine the starting point where destruction first occurs when receiving a shock. The thickness non-uniform structure may gradually become non-uniform towards the other end, or a thickness non-uniform structure may be formed by gradually (discontinuously) increasing the outer cylinder part region with a uniform thickness.

[0048] When the shock absorption members 20L, 20R, and 201 of the present invention have a thickness non-uniform structure such that the thickness increases from one end to the other end of the outer cylinder part, it is preferable that the thickness increase rate from one end to the other end is a positive value (however, it may include a part where the thickness increase rate is 0). That is, it is preferable that the thickness gradually increases from one end to the other end of the outer cylinder part (however, it may have a part with a constant thickness), and it is more preferable that there is no part where the thickness becomes thinner after once becoming larger.

[0049] Also, although there is no particular limitation on the degree of thickness non-uniformity, it is more preferable that the relationship between the thickness T1 of one end of the outer cylinder part and the thickness T2 of the other end is 1.0 < T2 / T1 < 3.0, and even more preferable that 1.0 < T2 / T1 < 2.0. Even when the outside flanges 40L and 40R are provided, the thickness of the other end T2 is the thickness of the other end of the outer cylinder part, and the thickness and size of the outside flanges 40L and 40R are not considered. Also, when manufacturing a shock absorption member provided with ribs or protrusions, these parts shall not be considered as part of the thickness.

[0050] [Resin] The resin contained in the impact absorbing member of the present invention will be described below. Furthermore, since the impact absorbing member is preferably a bonded body of a first member and a second member, the resin contained in the first member and / or the second member will also be described below. The resin may be thermosetting or thermoplastic.

[0051] 1.Thermoplastic resin When the resin used is a thermoplastic resin, the type is not particularly limited, and a resin having a desired softening point or melting point can be appropriately selected and used. As the thermoplastic resin, one having a softening point in the range of 180°C to 350°C is usually used, but is not limited thereto.

[0052] Examples of thermoplastic resins include polyolefin resins, polystyrene resins, polyamide resins, polyester resins, polyacetal resins (polyoxymethylene resins), polycarbonate resins, (meth)acrylic resins, polyarylate resins, polyphenylene ether resins, polyimide resins, polyethernitrile resins, phenoxy resins, polyphenylene sulfide resins, polysulfone resins, polyketone resins, polyether ketone resins, thermoplastic urethane resins, fluorine-based resins, and thermoplastic polybenzimidazole resins.

[0053] The impact absorbing member of the present invention may contain only one type of thermoplastic resin, or two or more types. Examples of a mode in which two or more types of thermoplastic resins are used in combination include, but are not limited to, a mode in which thermoplastic resins having different softening points or melting points are used in combination, or a mode in which thermoplastic resins having different average molecular weights are used in combination.

[0054] When a thermoplastic resin is used, it is more preferable to use a polyolefin resin, and even more preferable to use a polypropylene resin.

[0055] 2.Thermosetting resin The resin may be a thermosetting resin. When a thermosetting resin is used, it is preferably an unsaturated polyester resin, a vinyl ester resin, an epoxy resin, or a phenol resin. One type of resin may be used alone, or two or more types may be used in combination.

[0056] Furthermore, when a thermosetting resin is used as the resin of the present invention, it is preferable to use a sheet molding compound (sometimes called SMC) containing reinforcing fibers. Because of its high moldability, sheet molding compounds can be easily molded into even complex shapes. Sheet molding compounds have higher fluidity and formability than continuous fibers, making it easy to create ribs and bosses.

[0057] 3. Other agents The resin may contain additives such as various fibrous or non-fibrous fillers such as organic or inorganic fibers, flame retardants, UV-resistant agents, stabilizers, release agents, pigments, softeners, plasticizers, surfactants, etc. When a thermosetting resin is used, it may also contain thickeners, curing agents, polymerization initiators, polymerization inhibitors, etc. One type of additive may be used alone, or two or more types may be used in combination.

[0058] [Reinforced fiber] The reinforcing fibers contained in the impact absorbing member of the present invention will be described below. Furthermore, since the impact absorbing member is preferably a bonded body of a first member and a second member, the reinforcing fibers contained in the first member and / or the second member will also be described below.

[0059] 1. Fiber length The weight average fiber length of the reinforcing fibers is preferably 1 mm or more and 100 mm or less, more preferably 3 mm or more and 80 mm or less, and even more preferably 5 mm or more and 60 mm or less. In other words, the reinforcing fibers are preferably discontinuous fibers.

[0060] If the weight-average fiber length Lw of the reinforcing fibers is 100 mm or less, the flowability of the composite material is not likely to decrease when the first member and / or the second member are produced by press molding, and it is easy to produce them in the desired shape. Furthermore, if the weight-average fiber length Lw is 1 mm or more, the mechanical strength of the resulting first member and / or the second member is not likely to decrease, which is preferable.

[0061] When discontinuous fibers are used, formability is improved compared to when only continuous fibers are used, making it easier to create complex fiber-reinforced resin moldings. Furthermore, by using discontinuous reinforcing fibers, even if stress is applied from any direction to the first member and / or second member, it is unlikely that a direction in which the mechanical properties will be extremely weakened will occur.

[0062] In a molded product produced by injection molding, the weight-average fiber length of the reinforcing fibers is about 0.1 to 0.3 mm. Therefore, when the weight-average fiber length of the reinforcing fibers is set to 1 mm or more and 100 mm or less, it is preferable to produce a fiber-reinforced resin molded product by press molding.

[0063] In the present invention, discontinuous reinforcing fibers having different fiber lengths may be used in combination. In other words, the discontinuous reinforcing fibers used in the present invention may have a single peak in the weight-average fiber length distribution, or may have multiple peaks.

[0064] 2. Number-average fiber length Ln and weight-average fiber length Lw of reinforcing fibers Generally, if the fiber length of each reinforcing fiber is Li, the number average fiber length Ln and weight average fiber length Lw can be calculated by the following formulas (1) and (2). The units of the number average fiber length Ln and weight average fiber length Lw are mm. Ln=ΣLi / I equation (1) Lw=(ΣLi 2 ) / (ΣLi)...Equation (2) Here, "I" indicates the number of reinforcing fibers measured.

[0065] When the fiber length is constant, the number average fiber length and the weight average fiber length will be the same value. A sample can be taken from the impact absorbing component, and the reinforcing fibers can be extracted from it by, for example, subjecting it to a heat treatment at 500°C for about 1 hour and removing the resin in a furnace.

[0066] The average fiber length can be calculated, for example, by measuring the fiber lengths of 100 fibers randomly extracted from the impact absorbing member to the nearest 1 mm using a caliper or the like, and then calculating the average fiber length based on formula (1).

[0067] If the dispersion contains short fibers that cannot be measured with a caliper, remove the resin, then place the resulting reinforcing fibers in water containing a surfactant and thoroughly stir using ultrasonic vibrations. Samples for evaluation can be obtained by randomly sampling the stirred dispersion with a measuring spoon, and measuring the lengths of 3,000 fibers using a Nireco Luzex AP image analyzer. The measured fiber lengths can be used to calculate the number-average fiber length Ln and weight-average fiber length Lw using the same formulas (1) and (2) described above.

[0068] 3. Volume ratio of reinforcing fibers There is no particular limitation on the fiber volume fraction Vf of the reinforcing fibers in the impact absorbing member, but it is preferably 20 to 70%, more preferably 25 to 60%, and even more preferably 30 to 55%. The fiber volume fraction (Vf, unit: volume %) is the ratio of the volume of the reinforcing fibers to the total volume including not only the reinforcing fibers and resin but also other additives. There is no limitation on the analysis of the reinforcing fiber volume fraction, but it is recommended to measure it as follows.

[0069] A sample is cut out from the impact absorbing component (preferably from the first and / or second components constituting the impact absorbing component), and the resin is burned off in a furnace at 500°C for 1 hour. The mass of the sample before and after treatment is weighed to calculate the mass of the reinforcing fiber, resin, and other additives. Next, the volume ratio of the reinforcing fiber to the resin is calculated using the specific gravity of each component. Vf = 100 x reinforcing fiber volume / (reinforcing fiber volume + resin volume + other additive volume)

[0070] 4. Types of reinforcing fibers In this specification, the reinforcing fiber is preferably at least one selected from the group consisting of carbon fiber, aramid fiber, glass fiber, polyester fiber, nylon fiber, polypropylene fiber, and polyethylene fiber, and more preferably carbon fiber or glass fiber.

[0071] 4.1 Reinforcement fiber: carbon fiber 4.1.1. Carbon fiber in general When carbon fibers are used, polyacrylonitrile (PAN)-based carbon fibers, petroleum / coal pitch-based carbon fibers, rayon-based carbon fibers, cellulose-based carbon fibers, lignin-based carbon fibers, phenol-based carbon fibers, etc. are generally known, and any of these carbon fibers can be suitably used in the present invention. Among these, polyacrylonitrile (PAN)-based carbon fibers are preferred in the present invention because of their excellent tensile strength. As a PAN-based carbon fiber, for example, TENAX (registered trademark) STS40-24KS (average fiber diameter 7 μm) carbon fiber manufactured by Teijin Limited can be used.

[0072] 4.1.2. Carbon fiber sizing agent The carbon fiber used in the present invention may have a sizing agent attached to its surface. When using carbon fiber with a sizing agent attached, the type of sizing agent can be appropriately selected depending on the type of carbon fiber and the type of resin used in the X material or Y material, and is not particularly limited.

[0073] 4.2 Reinforcement fiber: glass fiber The case where the reinforcing fiber used in the present invention is glass fiber will be described. 4.2.1.Glass fiber in general The glass fiber used in the present invention may be any glass fiber generally referred to as glass fiber. The glass composition is not particularly limited, and may include A-glass, C-glass, E-glass, etc., and may contain components such as TiO2, SO3, and P2O5 in some cases. For example, Nitto Boseki's E-glass RS240QR-483 (count: 2400 g / 1000 m) glass fiber can be used as the glass fiber.

[0074] 4.2.2.Glass fiber sizing agents The glass fiber used in the present invention may have a sizing agent attached to its surface. When using glass fiber with a sizing agent attached, the type of sizing agent can be appropriately selected depending on the type of glass fiber and the type of resin, and is not particularly limited. Glass fiber that has been pre-treated with a conventionally known coupling agent such as an organosilane compound, an organotitanium compound, an organoborane compound, or an epoxy compound can be preferably used.

[0075] [Method of manufacturing the first member and / or the second member: molding die] The first member and the second member are made of reinforced fiber and resin, respectively. Preferably, the molded article is an integrally molded body produced by press-molding a composite material containing the above-mentioned components using a first mold and a second mold. Hereinafter, the first mold will be described as a lower mold (sometimes referred to as a molding lower mold), the second mold as an upper mold (sometimes referred to as a molding upper mold), and an upper mold that opens and closes by moving the second mold up and down toward the first mold. However, for example, the mold may also open and close by moving the first mold up and down toward the second mold. Alternatively, the mold may open and close by moving at least one of the first mold and the second mold horizontally.

[0076] [Method of manufacturing the first member and / or the second member: Press molding] 1. Hot press molding and cold press molding When producing the first member and / or the second member in the present invention, a composite material containing reinforcing fibers and a resin can be produced by press molding (sometimes called compression molding), and molding methods such as hot press molding and cold press molding can be used as the press molding. By press molding the composite material, various shapes can be imparted to the first member and / or the second member. The first member and / or the second member manufactured by press molding is preferably an integrally molded body.

[0077] 2.Cold press molding When a composite material containing a thermoplastic resin is used as the resin, press molding using cold press is preferred. In cold press molding, for example, a composite material heated to a first predetermined temperature is placed in a mold set to a second predetermined temperature, and then pressurized and cooled.

[0078] Specifically, if the thermoplastic resin contained in the composite material is crystalline, the first predetermined temperature is equal to or higher than the melting point, and the second predetermined temperature is lower than the melting point. If the thermoplastic resin is amorphous, the first predetermined temperature is equal to or higher than the glass transition temperature, and the second predetermined temperature is lower than the glass transition temperature. That is, the cold pressing method includes at least the following steps A-1) to A-2).

[0079] Step A-1) A step of heating the thermoplastic resin to a temperature above the melting point but below the decomposition temperature if the thermoplastic resin is crystalline, or above the glass transition temperature but below the decomposition temperature if the thermoplastic resin is amorphous. Step A-2) The composite material heated in step A-1) is placed in a mold whose temperature is adjusted to below the melting point if the thermoplastic resin is crystalline, or below the glass transition temperature if the thermoplastic resin is amorphous, and then pressurized. By performing these steps, the molding of the composite material can be completed (the first member and / or the second member, which are press-molded bodies, can be produced).

[0080] The above steps must be performed in the order described above, but other steps may be included between each step, such as a shaping step, which is performed before step A-2), in which a shaping mold different from the mold used in step A-2) is used to pre-shape the mixture into the shape of the cavity of the mold.

[0081] The shape of the composite material may be a shape developed by computer through inverse molding analysis from the three-dimensional shape of the press-molded product to be manufactured.

[0082] 3.Hot press molding In the hot press molding method, for example, a composite material is placed in a mold, pressure is applied while the temperature of the mold is raised to a first predetermined temperature, and the mold is cooled to a second predetermined temperature. Specifically, if the thermoplastic resin constituting the composite material is crystalline, the first predetermined temperature is equal to or higher than the melting point, and the second predetermined temperature is lower than the melting point. If the thermoplastic resin contained in the composite material is amorphous, the first predetermined temperature is equal to or higher than the glass transition temperature, and the second predetermined temperature is lower than the glass transition temperature. Hot press molding preferably includes at least the following steps B-1) to B-4).

[0083] B-1) A process of placing the composite material in the mold (second mold, lower mold). B-2) A process of applying pressure while heating the mold to a temperature above the melting point and below the thermal decomposition temperature of the thermoplastic resin if the thermoplastic resin is crystalline, or to a temperature above the glass transition temperature and below the thermal decomposition temperature of the thermoplastic resin if the thermoplastic resin is amorphous (first pressing process). B-3) A process of applying pressure in one or more stages, with the pressure in the final stage being 1.2 to 100 times the pressure in the first pressing process (second pressing process). B-4) A step of adjusting the mold temperature to below the melting point if the thermoplastic resin is crystalline, or below the glass transition temperature if the thermoplastic resin is amorphous. By carrying out these steps, an integrally molded structure can be produced.

[0084] 4. Commonalities between cold press molding and hot press molding Steps A-2) and B-3) are steps in which pressure is applied to the composite material to obtain a fiber-reinforced resin molded product of the desired shape. The molding pressure is not particularly limited, but is preferably as low as possible within a range that allows the desired shape of the first and / or second member to be obtained. Specifically, the pressure is preferably less than 30 MPa relative to the mold cavity projected area, more preferably 20 MPa or less, and even more preferably 10 MPa or less. A molding pressure of less than 30 MPa is preferable because it does not require capital investment or maintenance costs for a press. Naturally, various processes may be inserted between the above steps during compression molding; for example, vacuum compression molding, in which compression molding is performed under vacuum, may be used.

[0085] [Removal of molded product] It is preferable that the inside flange 202 has a uniform thickness (even thickness). If the inside flange 202 has a uniform thickness, the joining stability is improved when joining to the tip member 10, particularly when fastening with bolts or the like. This is because an inside flange 202 with a uniform thickness can be easily fastened using bolts and nuts.

[0086] When the flange to be joined to the tip member 10 is designed to have a uniform thickness, if the inside flange 202 provided at one end of the impact absorbing members 20L, 20R, 201 is designed as the outside flange 40L, 40R502, the outside flange 40L, 40R502 provided at one end will be dragged when the upper forming die 505 is lifted (when the forming die is opened) after the molding of the first member and / or second member is completed, as shown in Figure 5, and there is a risk that it will be rubbed and broken. If the outside flanges 40L, 40R502 are made unevenly thick and the vicinity of region 504 that will become the cylindrical portion when the impact absorbing members 20L, 20R, 201 are made thicker, the outside flanges 40L, 40R502 will not be dragged when the forming die is opened, but the stability of the joining (particularly fastening) will be reduced.

[0087] On the other hand, the cylindrical impact absorbing members 20L, 20R, and 201 of the present invention have an inside flange 202 at one end instead of an outside flange 40L, 40R, so the above-mentioned problem does not occur even if the inside flange 202 has a uniform thickness. For example, FIG. 4(B) shows a first or second member manufactured by press molding. FIG. 4(B) is a cross-sectional view taken along the X plane of FIG. 4(A). The first or second member (401 in FIG. 4) has regions that will become the inside flange 202, outside flanges 40L, 40R, and cylindrical portion when formed into the impact absorbing members 20L, 20R, and 201. FIG. 4(C) is a schematic diagram of the upper and lower molding dies used to manufacture the molded body of FIG. 4(B). A first member (or second member) 401 having an inside flange 402 of the shape shown in Figure 4(B) can be molded in a molding die as shown in Figure 4(C) by extending the inside flange 402 in the opposite direction to the extension of the outside flange 403, and the inside flange 402 will not be dragged when the upper molding die is pulled up.

[0088] It is more preferable that the first member and the second member are fiber-reinforced resin molded bodies, and that the first member and / or the second member does not have an undercut portion. [Explanation of symbols]

[0089] 10D: Bottom part 10U:Top part 10Fr: Front part 10Rr: Rear part 10: Tip member 20L, 20R, 201: Impact absorbing material 30L, 30R: Base end member 40L, 40R: Outside flange 100: Shock absorbing structure 202: Inside flange 203: Opening surface 204: End face 205: Outside flange 401: First member or second member 402: Area that becomes the inside flange when used as an impact absorbing member 403: Area that becomes the outside flange when used as an impact absorbing member 404: Area that becomes the cylindrical part when it becomes an impact absorbing member 405, 505: Upper mold 406, 506: Lower mold 501: First member or second member 502: Area that becomes the outside flange when used as an impact absorbing member 503: Area that becomes the outside flange when used as an impact absorbing member 504: Area that becomes the cylindrical part when it becomes a shock absorbing member 601: First side flange 602: Second side flange 701: Outer cylinder 702: Hollow part

Claims

1. A shock absorbing structure that absorbs impact energy, The shock absorbing structure includes a cylindrical shock absorbing member and a tip member, The cylindrical impact absorbing member has an inside flange at one end thereof, The cylindrical impact absorbing member and the tip member are joined via the inside flange. Impact absorbing structure.

2. 2. The shock absorbing structure according to claim 1, wherein an end face at one end of the cylindrical shock absorbing member is an open face that is at least partially open, and the inside flange extends toward the inside of the end face.

3. The shock absorbing structure according to claim 2 , wherein the inside flange extends along the end surface.

4. The shock absorbing structure includes a base member, An outside flange is provided at the other end of the cylindrical impact absorbing member, The shock absorbing structure according to claim 1 , wherein the cylindrical shock absorbing member and a base end member are joined via the outside flange.

5. The impact absorbing member includes reinforcing fibers having a weight average fiber length of 1 mm or more and 100 mm or less, and a resin, The orientation Tc of the reinforcing fibers contained in the cylindrical portion of the impact absorbing member, The orientation of the reinforcing fibers contained in the inside flange is set to Ti, 5. The shock absorbing structure according to claim 1, wherein the following is satisfied when the orientation of the reinforcing fibers in the outside flange is To: Tc < Ti Tc < To

6. The shock absorbing structure according to any one of claims 1 to 5, the impact absorbing member is a joined body of a first member having an open cross-sectional shape and a first side flange portion, and a second member having an open cross-sectional shape and a second side flange portion, The shock absorbing structure, wherein the first member and / or the second member is a reinforced fiber resin molding and is an integrally molded body having the inside flange.

7. The shock absorbing structure according to claim 6, The shock absorbing structure, wherein the first member and / or the second member is an integrally molded body having the outside flange.

8. 8. The shock absorbing structure according to claim 1, wherein the first member and / or the second member are arranged in order of increasing compressive strength from a front end side to a rear end side of the first member and / or the second member that receives an impact.

9. The impact absorbing member has a hollow structure consisting of an outer cylindrical portion and a hollow portion, The shock absorbing structure according to claim 1 , wherein the inside flange remains inside the hollow portion during a collision.

10. 10. The shock absorbing structure according to claim 1, wherein the inside flange has a uniform thickness.

11. The shock absorbing structure according to any one of claims 1 to 10, The shock absorbing structure is mounted on the vehicle, the tip member is disposed between an exterior body of a vehicle frame and the vehicle frame, The base end member is a vehicle frame member. Impact absorbing structure.

12. A method for manufacturing the shock absorbing structure according to claim 6, comprising the steps of: The first member and the second member are integrally molded bodies manufactured by press molding a composite material containing reinforcing fibers and a resin using a first mold and a second mold, respectively. A method for manufacturing a shock absorbing structure.

13. The method for manufacturing a shock absorbing structure according to claim 12, wherein the cylindrical shock absorbing member and the base end member are joined via the outside flange.

14. A method for manufacturing a shock absorbing structure according to claim 13, comprising the steps of: The first member and / or the second member do not have an undercut portion. A method for manufacturing a shock absorbing structure.

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