Vehicle impact absorbing components

Abstract

To provide a vehicle impact absorption member which can set with a higher degree of freedom, a structure of a vehicle impact absorption member which can highly efficiently absorb impact energy.SOLUTION: An impact absorption member 30 is formed of a resin material. The impact absorption member 30 has a cylindrical main body part 31 and an intermediate wall part 32. The intermediate wall part 32 is arranged in an intermediate position of the main body part 31 in an axial line direction in the main body part 31, and extends in a direction intersecting with the axial line direction. The main body part 31 has a fracture part 35 which fractures when being buckled and deformed by an axial load. The fracture part 35 extends along a boundary portion between the main body part 31 and the intermediate wall part 32.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an impact absorbing member for a vehicle. [Background technology]

[0002] A commonly used vehicle impact absorbing component has a cylindrical main body made of a metal material (see, for example, Patent Document 1). In this vehicle impact absorbing component, when an axial load acts on the main body, the main body undergoes buckling deformation in a bellows-like manner. Impact energy is absorbed by this deformation of the main body.

[0003] Patent Document 2 discloses that the cylindrical main body is made of a resin material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2-175452 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-175430 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned vehicle impact absorbing component, when the main body undergoes buckling deformation under an axial load, the main body is folded like an accordion and becomes stacked in the direction of the axis (hereinafter referred to as the "axial direction"). As the buckling deformation of the main body progresses, the main body reaches a so-called bottoming-out state, where further buckling deformation is prevented by the stacked main body. In this way, in the above-mentioned vehicle impact absorbing component, the amount of axial deformation (hereinafter referred to as the "deformation stroke") caused by the buckling deformation of the main body is determined by the amount of deformation of the main body from a non-buckling state to the bottoming-out state.

[0006] Typically, under the same conditions of the plate thickness of the body, the strength of a resin body is lower than that of a metal body. Therefore, when a resin body is used, the plate thickness of the body is greater than when a metal body is used. Therefore, when a resin body is used, the amount of deformation of the body before bottoming out is reduced by the amount of the greater plate thickness of the body. This shortens the deformation stroke of the body, which reduces the degree of freedom in designing the structure of a vehicle impact absorbing component to achieve efficient impact energy absorption. [Means for solving the problem]

[0007] The vehicle impact absorbing component for solving the above problem is a vehicle impact absorbing component formed from a resin material, and comprises a cylindrical main body portion and an intermediate wall portion that is provided at an intermediate position in the axial direction of the main body portion within the main body portion and extends in a direction intersecting the axial direction, and the main body portion has a breaking portion that breaks when buckling deformation occurs due to an axial load, and the breaking portion extends along the boundary between the main body portion and the intermediate wall portion. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional plan view of a vehicle impact absorbing member according to a first embodiment. [Figure 2] FIG. 2 is a plan view of the impact absorbing member for a vehicle. [Figure 3] 3 is a view of the impact absorbing member for a vehicle taken along the arrow 3 in FIG. 2. [Figure 4] FIG. 2 is a plan view of the impact absorbing member for a vehicle in the early stage of deformation. [Figure 5] FIG. 2 is a plan view of the impact absorbing member for a vehicle in the middle stage of deformation. [Figure 6] FIG. 2 is a flat end view of the vehicle impact absorbing member in a broken state. [Figure 7] 3 is a plan view of the impact absorbing member for a vehicle in a bottomed state. FIG. [Figure 8]4 is a graph showing the results of a compression test on the impact absorbing member for a vehicle of the first embodiment and an impact absorbing member of a comparative example. [Figure 9] FIG. 6 is a cross-sectional plan view of a vehicle impact absorbing member according to a second embodiment. [Figure 10] 10 is a cross-sectional view of the impact absorbing member for a vehicle taken along line 10-10 in FIG. 9. [Figure 11] 3 is a cross-sectional plan view of a groove and its periphery in the impact absorbing member for a vehicle. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) Hereinafter, a shock absorbing member for a vehicle according to a first embodiment (hereinafter referred to as a shock absorbing member 30) will be described with reference to FIGS.

[0010] Hereinafter, the fore-and-aft direction of the vehicle will be referred to as the fore-and-aft direction L, the width direction of the vehicle as the vehicle width direction W, and the up-and-down direction of the vehicle when the vehicle is positioned on a horizontal plane as the up-and-down direction Z. Furthermore, the front and rear sides in the fore-and-aft direction L will be referred to simply as the "front side" and the "rear side", respectively, and the upper and lower sides in the up-and-down direction Z will be referred to simply as the "upper side" and the "lower side", respectively.

[0011] 1, provided at the front of the vehicle are, in order from the front, a bumper reinforcement 20, an impact absorbing member 30, and a front side member 21. That is, the impact absorbing member 30 is sandwiched between the bumper reinforcement 20 and the front side member 21 in the front-rear direction L.

[0012] Each component of the impact absorbing member 30 will be described in detail below. 1 to 3, the impact absorbing member 30 has a main body portion 31, an intermediate wall portion 32, and a base portion 33. The main body portion 31, the intermediate wall portion 32, and the base portion 33 are integrally molded from a synthetic resin material.

[0013] <Main body> The main body 31 has a generally regular octagonal cylindrical shape. The axis of the main body 31 extends in the front-rear direction L. The front end of the main body 31 is not closed and is open toward the front. In this embodiment, one end of the main body 31 in the axial direction, more specifically the front end of the main body 31, forms a load receiving portion 34 that receives an axial load.

[0014] <Intermediate wall> The intermediate wall portion 32 is provided inside the main body portion 31. The intermediate wall portion 32 is provided at a central position in the front-to-rear direction L of the main body portion 31. The intermediate wall portion 32 has a flat plate shape extending in a direction perpendicular to the axial direction of the main body portion 31, i.e., in the up-down direction Z and the vehicle width direction W. The intermediate wall portion 32 divides the interior of the main body portion 31 into a space on the load receiving portion 34 side and a space on the side remote from the load receiving portion 34.

[0015] The impact absorbing member 30 is molded using a mold device (not shown) having a movable mold and a fixed mold. In this embodiment, the mating surface between the movable mold and the fixed mold (so-called parting line) is set at the center position in the front-rear direction L of the main body 31, i.e., the position where the intermediate wall 32 is disposed.

[0016] <Breakage part> The main body 31 has a breaking portion 35. The breaking portion 35 is a portion that breaks when the main body 31 buckles due to an axial load. The breaking portion 35 extends in the circumferential direction of the main body 31 along the boundary between the main body 31 and the intermediate wall 32. The breaking portion 35 extends around the entire periphery of the main body 31.

[0017] In the impact absorbing member 30 of this embodiment, when the main body portion 31 breaks at the breaking portion 35, the main body portion 31 is divided into a front portion including the intermediate wall portion 32 (hereinafter referred to as the "first portion P1") and a rear portion not including the intermediate wall portion 32 (hereinafter referred to as the "second portion P2").

[0018] In this embodiment, the material for forming the impact absorbing member 30 and the thickness of each component of the impact absorbing member 30 that will achieve the above-described fracture mode are determined in advance based on the results of various experiments and simulations conducted by the inventors. The determined material and thickness are then set as the material for forming the impact absorbing member 30 and the thickness of each component of the impact absorbing member 30. In this embodiment, polybutylene terephthalate (PBT) is used as the material for forming the impact absorbing member 30. The thicknesses of the main body 31 and the intermediate wall 32 are set to be 3 mm or more and 4 mm or less. The material for forming the impact absorbing member 30 and the thickness of each component of the impact absorbing member 30 can be changed as desired, as long as the above-described fracture mode is achieved.

[0019] <Base> The pedestal portion 33 is provided at the rear end of the main body portion 31. The pedestal portion 33 has a flat plate shape extending in the vehicle width direction W and the up-down direction Z. The pedestal portion 33 has a substantially square outer shape in a plan view. An opening 37 penetrating the pedestal portion 33 in the front-to-rear direction L is provided in a central portion of the pedestal portion 33 in a plan view, more specifically, in a portion corresponding to the rear side of the main body portion 31. In the impact absorbing member 30 of this embodiment, the rear end of the main body portion 31 is not blocked by the pedestal portion 33, but opens rearward via the opening 37. Through holes 38 penetrating the pedestal portion 33 in the front-to-rear direction L are provided at four corners of the pedestal portion 33. Bolts (not shown) for fixing the pedestal portion 33 to the front end surfaces of the front side members 21 are inserted into the through holes 38.

[0020] <effect> The action of the impact absorbing member 30 of this embodiment will be described below. When a vehicle collides head-on, a load caused by the collision (hereinafter referred to as a collision load) acts on the load receiving portion 34 that constitutes the front end of the main body portion 31 via the bumper reinforcement 20.

[0021] As shown in Fig. 4, when a collision load is applied in this manner, the main body 31 undergoes buckling deformation in a manner that gradually takes on an accordion-like shape, starting from the front end. In this embodiment, the front end of the main body 31 is open. This makes the front portion of the main body 31 more susceptible to deformation due to the axial load than a structure in which the front end of the main body 31 is closed, and therefore reduces the initial load when a collision load is applied.

[0022] 5, the buckling deformation of the main body 31 then progresses and reaches the portion where the intermediate wall 32 is provided. The portion where the intermediate wall 32 is provided has a structure in which the main body 31 is supported by the intermediate wall 32. Therefore, it can be said that the portion of the main body 31 where the intermediate wall 32 is provided has higher rigidity than other portions of the main body 31. Therefore, when the buckling deformation of the main body 31 reaches the portion where the intermediate wall 32 is provided, the collision load is received by the portion where the intermediate wall 32, i.e., the portion having a relatively high rigidity, and the collision load temporarily increases.

[0023] In the impact absorbing member 30 of this embodiment, by changing the position of the intermediate wall portion 32 in the front-rear direction L relative to the main body portion 31, it is possible to change the timing at which the buckling deformation of the main body portion 31 reaches the portion where the intermediate wall portion 32 is disposed. This makes it possible to change the timing at which the collision load acting on the impact absorbing member 30 increases. In this way, in the impact absorbing member 30 of this embodiment, it is possible to adjust the manner in which the collision load changes during the deformation process of the main body portion 31 by adjusting the position of the intermediate wall portion 32.

[0024] As the deformation of the main body 31 progresses, the portion of the main body 31 rearward of the intermediate wall 32 undergoes buckling deformation, as indicated by the two-dot chain line in Fig. 5. At the beginning of this deformation, the portion of the main body 31 rearward of the intermediate wall 32 deforms in a manner that widens toward the rear, as indicated by arrow A1 in Fig. 5. Meanwhile, tensile stress acts on the intermediate wall 32, which supports the main body 31 from the inside, as indicated by arrow A2 in Fig. 5. Therefore, at this time, stress is concentrated at the corner 36 that forms the boundary between the main body 31 and the intermediate wall 32.

[0025] 6, as the deformation of the main body 31 progresses further, a large stress generated by the concentration of stress at the corner 36 causes the main body 31 to break starting from the corner 36. This break causes the main body 31 to be divided into a first portion P1, which is the front portion including the intermediate wall 32, and a second portion P2, which is the rear portion not including the intermediate wall 32.

[0026] 7, after the main body 31 is broken, the first portion P1 including the intermediate wall 32 enters the inside of the second portion P2, pushing open the front end of the second portion P2 that does not include the intermediate wall 32. By deforming the main body 31 in this manner, the front part of the second portion P2 can be retracted to a position where it does not overlap with the first portion P1 in the front-rear direction L, as shown by arrow A3 in FIG.

[0027] In the impact absorbing member 30 of this embodiment, when the main body portion 31 buckles and deforms due to a collision load, the main body portion 31 is folded like an accordion and stacked in the front-to-rear direction L. However, in the impact absorbing member 30, the front portion of the second portion P2 is retracted to a position where it does not overlap with the first portion P1, and therefore the front portion of the second portion P2 is no longer stacked. This increases the amount of deformation of the main body portion 31 from a non-buckling state to the bottoming-out state, i.e., the deformation stroke. Therefore, the structure of the impact absorbing member 30 can be designed with a high degree of freedom to achieve efficient impact energy absorption.

[0028] As the deformation of the main body 31 progresses further, the rear portion of the second portion P2 is pressed by the first portion P1, causing buckling deformation. After that, the impact absorbing member 30 reaches a state where the stacked main body 31 prevents further buckling deformation of the main body 31, that is, a bottomed-out state (the state shown in FIG. 7).

[0029] Next, with reference to FIG. 8, the results of the compression test on the impact absorbing member 30 of this embodiment and the impact absorbing member of the comparative example will be described. In FIG. 8, the solid line indicates the load-displacement curve for the impact absorbing member 30 of this embodiment.

[0030] 8, the dashed line indicates the load-displacement curve for the impact absorbing member of Comparative Example 1. The impact absorbing member of Comparative Example 1 differs from impact absorbing member 30 of this embodiment in that the front end of main body 31 is closed and that it does not have intermediate wall 32.

[0031] 8, the dashed dotted line indicates the load-displacement curve of the impact absorbing member of the second comparative example. The impact absorbing member of the second comparative example differs from the impact absorbing member 30 of this embodiment in that it does not have the intermediate wall portion 32.

[0032] 8, according to the impact absorbing member 30 of this embodiment (solid line), the initial load is reduced to about three-fifths of that of the impact absorbing member of the first comparative example (dashed line). This is thought to be because the front end of the main body 31 of the impact absorbing member of the first comparative example is closed, whereas the front end of the main body 31 of the impact absorbing member 30 of this embodiment is open.

[0033] 8, in the impact absorbing member of the first comparative example (dashed line) and the impact absorbing member of the second comparative example (chain line), the impact load acting on the impact absorbing member gradually increases in the middle of the deformation process of the main body portion 31. In contrast, in the impact absorbing member 30 of this embodiment (solid line), the impact load temporarily increases in the middle of the deformation process of the main body portion 31. This is thought to be because the impact absorbing member of the first comparative example and the impact absorbing member of the second comparative example do not have the intermediate wall portion 32, whereas the impact absorbing member 30 of this embodiment does have the intermediate wall portion 32.

[0034] 8, the maximum displacement, i.e., the deformation stroke, of the impact absorbing member 30 of this embodiment (solid line) is larger than that of the impact absorbing member of the first comparative example (dashed line) and the impact absorbing member of the second comparative example (chain line). This is thought to be because the impact absorbing member of the first comparative example and the impact absorbing member of the second comparative example do not have the intermediate wall portion 32 and the breaking portion 35, whereas the impact absorbing member 30 of this embodiment does have the intermediate wall portion 32 and the breaking portion 35.

[0035] <Effects> According to this embodiment, the following effects can be obtained. (1-1) The main body 31 has a breaking portion 35 that breaks when buckling deformation occurs due to an axial load. The breaking portion 35 extends along the boundary between the main body 31 and the intermediate wall 32. This allows the deformation stroke to be increased, and therefore the structure of the impact absorbing member 30 can be designed with a high degree of freedom to achieve efficient absorption of impact energy.

[0036] (Second embodiment) Hereinafter, the shock absorbing member for a vehicle according to the second embodiment (hereinafter referred to as the shock absorbing member 40) will be described with reference to FIGS. 9 to 11, focusing on the differences from the first embodiment.

[0037] The impact absorbing member 40 of this embodiment differs from the impact absorbing member 30 of the first embodiment only in that it has a weak portion that is weaker than other portions. The weak part will be described in detail below.

[0038] In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and redundant explanations of these components will be omitted. <Weakened parts> 9 to 11, the impact absorbing member 40 of this embodiment has a V-groove-shaped groove 41. The groove 41 extends in the circumferential direction of the main body portion 31 along the boundary between the main body portion 31 and the intermediate wall portion 32. More specifically, the groove 41 extends around the entire periphery of the intermediate wall portion 32 at the outer edge of the intermediate wall portion 32. The groove 41 is provided on the surface of the intermediate wall portion 32 that is farther from the load-receiving portion 34, i.e., on the rear surface of the intermediate wall portion 32. In this embodiment, the groove 41 corresponds to a weak portion that is weaker than other portions of the boundary portion.

[0039] <effect> The effects of the impact absorbing member 40 of this embodiment will be described below. In the impact absorbing member 40 of this embodiment, when the buckling deformation of the main body 31 progresses after reaching the portion where the intermediate wall 32 is disposed, the portion of the main body 31 rearward of the intermediate wall 32 undergoes buckling deformation. At this time, as shown by the two-dot chain line in Fig. 11 , the portion of the main body 31 rearward of the intermediate wall 32 deforms in a manner that widens toward the rear. As the main body 31 deforms in this manner, the grooves 41 provided on the outer edge of the intermediate wall 32 widen toward the outer periphery. As a result, stress is concentrated at the bottom (more specifically, the corners) of the V-shaped grooves 41.

[0040] In the impact absorbing member 40, as deformation of the main body portion 31 progresses further, a large stress generated by the concentration of stress at the bottom of the groove 41 causes the main body portion 31 to tear, starting from the bottom of the groove 41. As a result, the main body portion 31 breaks at the breaking portion 35. This break divides the main body portion 31 into a first portion P1, which is the front portion including the intermediate wall portion 32, and a second portion P2, which is the rear portion not including the intermediate wall portion 32.

[0041] In the impact absorbing member 40, a groove 41 is formed as a weakened portion at the boundary between the main body portion 31 and the intermediate wall portion 32. Therefore, the main body portion 31 can be broken at a pre-determined position (specifically, breaking portion 35) starting from this groove 41. This makes it possible to precisely control the deformation mode of the main body portion 31.

[0042] <Effects> According to this embodiment, in addition to the effect similar to the effect described in (1-1) above, the following effects described in (2-1) to (2-3) can be obtained.

[0043] (2-1) The groove 41 as the weakened portion is provided at the boundary between the main body portion 31 and the intermediate wall portion 32. Therefore, the deformation of the main body portion 31 can be controlled with high precision.

[0044] (2-2) The groove 41 is formed in the intermediate wall portion 32 so as to extend in the circumferential direction of the main body portion 31. Therefore, the main body portion 31 can be broken at a predetermined position starting from the groove 41.

[0045] (2-3) The groove 41 is provided on the rear surface of the intermediate wall portion 32. Therefore, the main body portion 31 can be divided into a first portion P1, which is a front portion including the intermediate wall portion 32, and a second portion P2, which is a rear portion not including the intermediate wall portion 32. As a result, after the main body portion 31 is broken, the front second portion P2 can push out the rear first portion P1, thereby deforming the main body portion 31.

[0046] <Example of change> The above-described embodiments can be modified as follows: The above-described embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0047] The groove 41 in the second embodiment is not limited to a V-shaped groove, but may be a U-shaped groove, a rectangular groove, a semicircular groove, or any other shape.

[0048] In the second embodiment, instead of the groove 41 extending over the entire periphery of the main body 31, grooves extending intermittently in the circumferential direction of the main body 31 may be provided. In the second embodiment, a plurality of recesses may be provided instead of the groove 41. In this configuration, for example, the plurality of recesses may be provided in a manner that they are spaced apart in the circumferential direction of the main body portion 31 and that they are arranged along the boundary portion between the main body portion 31 and the intermediate wall portion 32. In this configuration, the plurality of recesses correspond to the fragile portion.

[0049] Alternatively, it is possible to provide a plurality of through holes that penetrate the intermediate wall portion 32 in the front-rear direction L, spaced apart in the circumferential direction of the main body portion 31 and aligned along the boundary between the main body portion 31 and the intermediate wall portion 32. In this configuration, the plurality of through holes correspond to the fragile portion.

[0050] In the second embodiment, the groove 41 or recess serving as the weakened portion may be provided on the front surface of the intermediate wall portion 32, which is the surface facing the load-receiving portion 34. This configuration allows the main body portion 31 to be divided into a first portion, which is the front portion not including the intermediate wall portion 32, and a second portion, which is the rear portion including the intermediate wall portion 32. Therefore, after the main body portion 31 breaks, the front end portion of the rear second portion pushes and spreads the rear end portion of the front first portion, thereby deforming the main body portion 31. This allows the rear portion of the first portion to be retracted to a position where it does not overlap with the second portion in the front-to-rear direction L.

[0051] In the second embodiment, the main body 31 may be provided with a groove (or a recess) as a weakened portion. In each embodiment, the position of the intermediate wall portion 32 inside the main body portion 31 can be any position other than the center position in the front-to-back direction L of the main body portion 31, as long as it is the middle position in the front-to-back direction L of the main body portion 31.

[0052] In each embodiment, the direction in which the intermediate wall portion 32 extends can be any direction other than a direction perpendicular to the axial direction of the main body portion 31, as long as it intersects with the axial direction of the main body portion 31.

[0053] In each embodiment, the intermediate wall portion 32 may be provided with a through-hole or a thin-walled portion that is thinner than other portions. According to this configuration, the rigidity of the intermediate wall portion 32 can be adjusted by providing a through-hole or a thin-walled portion, so that the deformation mode and impact load of the impact absorbing members 30, 40 can be set with a high degree of freedom.

[0054] In each embodiment, the thickness of each portion of the main body 31 and the thickness of each portion of the intermediate wall 32 can be changed as desired. For example, the thickness of the front portion of the main body 31 can be set to different values, such as by making the rear portion thinner than the front portion of the main body 31. The thickness of the main body 31 and the intermediate wall 32 can also be set to different values, such as by making the thickness of the intermediate wall 32 thinner than the thickness of the main body 31. It is also possible to gradually change the thickness of the main body 31, such as by making the thickness of the front portion of the main body 31 thinner toward the load-receiving portion 34. This configuration allows the rigidity of each portion of the main body 31 and the intermediate wall 32 to be adjusted with a high degree of freedom, thereby allowing the deformation pattern and impact load of the impact-absorbing members 30, 40 to be set with a high degree of freedom.

[0055] The impact absorbing member having the above configuration is preferably molded from a synthetic resin material using a mold device, similar to the impact absorbing members 30 and 40 according to each embodiment. By forming the impact absorbing member in this manner, it is possible to easily form an impact absorbing member having a structure in which the plate thickness of each portion of the main body portion 31 and the plate thickness of each portion of the intermediate wall portion 32 are different, compared to when the impact absorbing member is formed from a metal material.

[0056] In each embodiment, reinforcing ribs may be provided on the inner or outer surface of the main body 31. In each embodiment, instead of forming the main body 31 into a generally regular octagonal cylindrical shape, it may be formed into a cylindrical shape of any desired shape, such as a hexagonal cylindrical shape, a square cylindrical shape, a circular cylindrical shape, or an elliptical cylindrical shape. [Explanation of symbols]

[0057] P1…first part P2…Second part 20...Bumper reinforcement 21...Front side member 30...Shock absorbing member 31...Main body 32...Intermediate wall 33...Base 34...Load receiving part 35...Fracture 36...Corner 37...Opening 38...Through hole 40...Shock absorbing member 41...Groove

Claims

1. A vehicle impact absorbing member formed of a resin material, A cylindrical main body; an intermediate wall portion provided inside the main body portion at an intermediate position in the axial direction of the main body portion and extending in a direction intersecting the axial direction, the main body portion has a breaking portion that breaks when buckling deformation occurs due to an axial load, The breaking portion extends along the boundary between the main body portion and the intermediate wall portion. Impact absorbing components for vehicles.

2. The boundary portion is provided with a weak portion that is weaker than other portions of the boundary portion. The impact absorbing member for a vehicle according to claim 1 .

3. The weakened portion is a groove formed in the main body portion or the intermediate wall portion and extending in the circumferential direction of the main body portion. The impact absorbing member for a vehicle according to claim 2.

4. One end of the main body in the axial direction constitutes a load receiving portion that receives the axial load, The groove is provided on a surface of the intermediate wall portion farther from the load receiving portion. The impact absorbing member for a vehicle according to claim 3.

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