Shock Absorbing Structure and Method for Manufacturing Shock Absorbing Structure

Abstract

To provide an impact absorption structure that can stably receive impact load without a decrease in the amount of absorbed impact energy, and a method for producing an impact absorption structure.SOLUTION: An impact absorption structure 10 extends in a predetermined extension direction. A first end 10a in the extension direction of the impact absorption structure 10 has an inclined slope 11 that is inclined relative to a plane P vertical to the extension direction. The inclined slope 11 has an inclination angle θ relative to the plane P, which varies in the extension direction. The impact absorption structure 10 maintains a constant thickness in the extension direction.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a shock absorption structure and a method for manufacturing the shock absorption structure.

Background Art

[0002] A shock absorption structure extending in a predetermined extending direction is provided in a vehicle or the like. When the vehicle collides with an object, a shock load acts on the shock absorption structure. The shock absorption structure absorbs shock energy by deforming when receiving the shock load in the extending direction. At this time, if no starting point of deformation is provided in the shock absorption structure, it becomes difficult for the shock absorption structure to stably receive the shock load by being compressed and destroyed. Therefore, it is preferable that the shock absorption structure is provided with a starting point of deformation so as to deform in order from the end in the extending direction. For example, in the shock absorption structure described in Patent Document 1, a starting point of deformation is provided at the end of the shock absorption structure by gradually thinning the plate thickness of the end in the extending direction toward the tip.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, when no starting point of deformation is provided in the shock absorption structure, the shock load received by the shock absorption structure during a collision increases rapidly. On the other hand, when a starting point of deformation is provided by thinning the plate thickness at the end of the shock absorption structure, the cross-section perpendicular to the extending direction, that is, the area of the surface receiving the shock load, becomes smaller at the end of the shock absorption structure. For this reason, the shock load received by the shock absorption structure during a collision increases gently compared to the case where no starting point of deformation is provided. As a result, the amount of absorbed shock energy decreases. Then, depending on the amount of shock energy to be absorbed, it is necessary to increase the length of the shock absorption structure. When the length of the shock absorption structure increases, the weight of the shock absorption structure increases.

Means for Solving the Problems

[0005] The shock absorption structure for solving the above problems is a shock absorption structure extending in a predetermined extending direction, wherein an end portion in the extending direction has an inclined surface inclined with respect to a plane perpendicular to the extending direction, and an inclination angle of the inclined surface with respect to the plane changes in the extending direction, and the thickness of the shock absorption structure is constant in the extending direction.

[0006] The end portion in the extending direction of the shock absorption structure has an inclined surface. For this reason, by the end portion having the inclined surface serving as a starting point of deformation, the shock absorption structure can be deformed in order from the end portion. Further, the thickness of the shock absorption structure is constant in the extending direction. That is, a starting point of deformation is provided to the shock absorption structure without thinning the thickness of the shock absorption structure. For this reason, it is suppressed that the cross-section perpendicular to the extending direction of the shock absorption structure, that is, the area of the surface receiving the shock load, becomes smaller as in the prior art. Therefore, the shock load received by the shock absorption structure during a collision increases rapidly. Thus, the shock absorption structure can stably receive the shock load without reducing the amount of absorbed shock energy.

[0007] Furthermore, the inclination angle of the inclined surface with respect to the plane perpendicular to the extending direction changes in the extending direction. As a result, compared with the case where the inclination angle of the inclined surface with respect to the plane perpendicular to the extending direction does not change, the maximum value of the impact load received by the shock-absorbing structure at the initial stage of deformation approaches the average value of the impact load received by the shock-absorbing structure in the subsequent deformation process. Therefore, when the shock-absorbing structure is provided in a vehicle, a sudden deceleration of the vehicle during a collision is suppressed. As a result, the impact received by the vehicle occupants during a collision can be reduced.

[0008] In the shock-absorbing structure, the inclination angle of the inclined surface with respect to the plane may gradually change in the extending direction. With this configuration, the impact received by the vehicle occupants during a collision can be further reduced.

[0009] In the shock-absorbing structure, the inclined surface has a first surface and a second surface located on the tip side of the first surface in the extending direction, and the inclination angle of the second surface with respect to the plane may be smaller than the inclination angle of the first surface with respect to the plane.

[0010] With this configuration, compared with the case where the inclination angle of the second surface with respect to the plane is larger than the inclination angle of the first surface with respect to the plane, the area of the cross-section perpendicular to the extending direction on the second surface can be increased. Therefore, the amount of absorbed impact energy can be increased.

[0011] A method for manufacturing a shock-absorbing structure for solving the above problems is a method for manufacturing a shock-absorbing structure having a cylindrical shape and expanding in diameter in the axial direction, the method including a cutting step of cutting a fabric having a constant thickness, and a forming step of forming the fabric cut in the cutting step into a cylindrical shape by rolling it. In the cutting step, the fabric is cut into a shape having a first side extending linearly, a second side longer than the first side, and a pair of third sides connecting the first side and the second side. In the forming step, the cut fabric is rolled so that the pair of third sides face each other.

[0012] In the cutting process, the first side of the fabric is cut so as to extend linearly, and in the forming process, the cut fabric is formed into a cylindrical shape such that a pair of third sides face each other. For this reason, the first side becomes an inclined surface that is inclined with respect to a plane perpendicular to the axial direction at the axial end of the shock-absorbing structure and the inclination angle with respect to the plane gradually changes in the axial direction. Further, the thickness of the fabric becomes the thickness of the shock-absorbing structure. Since the thickness of the fabric is constant, the thickness of the shock-absorbing structure is constant in the axial direction.

[0013] In this case, by having the end portion with the inclined surface as the starting point of deformation, the shock-absorbing structure can be deformed in order from the end portion. Further, a starting point of deformation can be provided in the shock-absorbing structure without reducing the thickness of the shock-absorbing structure. For this reason, it is possible to suppress a decrease in the area of a cross section perpendicular to the axial direction of the shock-absorbing structure, that is, the area of the surface that receives the impact load, as in the prior art. Therefore, the impact load received by the shock-absorbing structure at the time of collision rapidly increases. Thus, the shock-absorbing structure can stably receive the impact load without reducing the amount of absorbed shock energy. Further, compared with the case where the inclination angle of the inclined surface with respect to the plane perpendicular to the axial direction does not change, the maximum value of the impact load received by the shock-absorbing structure at the initial stage of deformation approaches the average value of the impact load received by the shock-absorbing structure in the subsequent deformation process. Therefore, when the shock-absorbing structure is provided in a vehicle, a rapid deceleration of the vehicle at the time of collision is suppressed. As a result, the impact received by the vehicle occupants at the time of collision can be reduced.

[0014] In the method for manufacturing the shock-absorbing structure, by devising the cutting shape of the fabric, an inclined surface can be provided at the axial end of the shock-absorbing structure simply by rounding the cut fabric into a cylindrical shape. In this case, processing such as cutting the end portion in order to provide a starting point of deformation at the end portion of the shock-absorbing structure is unnecessary. Therefore, the productivity of the shock-absorbing structure is improved and the material yield of the shock-absorbing structure is improved.

Effects of the Invention

[0015] According to the present invention, it is possible to stably receive an impact load without reducing the amount of absorbed impact energy.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

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Figure 10

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Figure 16

Modes for Carrying Out the Invention

[0017] Hereinafter, an embodiment in which the shock absorption structure and the method for manufacturing the shock absorption structure are embodied will be described with reference to FIGS. 1 to 5. The shock absorption structure of this embodiment is provided in the front of the vehicle. In the following description, front, rear, left, and right refer to the front, rear, left, and right when the driver of the vehicle is facing forward (the forward direction).

[0018] As shown in FIG. 1, in a vehicle, a front cross member 120 is provided between a pair of front side members 110 provided on both sides in the left-right direction. The front cross member 120 connects the pair of front side members 110. At the front end portions of the pair of front side members 110, shock absorption structures 10 are respectively provided so as to support the front bumper 130.

[0019] The shock absorption structure 10 is formed of a fiber reinforced composite material described later. The shock absorption structure 10 extends in a predetermined extending direction. The shock absorption structure 10 of this embodiment extends along the front-rear direction. Therefore, the predetermined extending direction in this embodiment is the front-rear direction. When the vehicle collides with an object, more specifically, when the front bumper 130 collides with an object, a shock load acting rearward is applied to the shock absorption structure 10 via the front bumper 130. The shock absorption structure 10 absorbs shock energy by deforming when receiving the shock load.

[0020] <Configuration of the shock absorption structure> As shown in FIG. 2, the shock absorption structure 10 of this embodiment has a cylindrical shape. When the shock absorption structure 10 has a cylindrical shape, the axial direction of the shock absorption structure 10 coincides with the extending direction. That is, the axial direction of the shock absorption structure 10 of this embodiment coincides with the front-rear direction. The cross-sectional shape perpendicular to the axial direction of the shock absorption structure 10 is circular.

[0021] The shock absorber structure 10 has a first end portion 10a and a second end portion 10b. The first end portion 10a and the second end portion 10b are axial end portions of the shock absorber structure 10. The second end portion 10b is an end portion located opposite to the first end portion 10a in the axial direction of the shock absorber structure 10. In the present embodiment, the first end portion 10a is the front end portion of the shock absorber structure 10. Also, the second end portion 10b is the rear end portion of the shock absorber structure 10. The diameter of the shock absorber structure 10 of the present embodiment gradually increases from the first end portion 10a toward the second end portion 10b in the axial direction.

[0022] A first bracket 21 made of metal is attached to the first end portion 10a. The first bracket 21 is fixed to the shock absorber structure 10 in a state of being inserted inside the first end portion 10a. In the present embodiment, a bolt (not shown) passing through the front bumper 130 is screwed into the female screw hole 21a of the first bracket 21. Thereby, the shock absorber structure 10 is attached to the front bumper 130 via the first bracket 21.

[0023] A second bracket 22 made of metal is attached to the second end portion 10b. The second bracket 22 is fixed to the outer peripheral surface of the shock absorber structure 10. In the present embodiment, a bolt (not shown) inserted through the through hole 22a of the second bracket 22 is screwed into a female screw hole (not shown) formed in the front side member 110. Thereby, the shock absorber structure 10 is attached to the front side member 110 via the second bracket 22.

[0024] As shown in FIG. 3, the first end portion 10a of the shock absorber structure 10 has an inclined surface 11. The inclined surface 11 is a surface inclined with respect to a plane P perpendicular to the extending direction. The inclination angle θ of the inclined surface 11 with respect to the plane P changes in the extending direction.

[0025] The inclined surface 11 has a first end 11a and a second end 11b. The first end 11a and the second end 11b are the ends of the inclined surface 11 in the extending direction. The second end 11b is located on the tip side relative to the first end 11a. The inclined surface 11 of the present embodiment is curved so as to bulge on the tip side of a virtual straight line L connecting the first end 11a and the second end 11b in a side view seen from a direction orthogonal to the extending direction. Therefore, the inclination angle θ of the inclined surface 11 with respect to the plane P changes gradually. Specifically, the inclination angle θ of the inclined surface 11 with respect to the plane P gradually decreases from the first end 11a toward the second end 11b.

[0026] As shown in FIG. 4, the thickness T10 of the shock absorption structure 10 is constant in the axial direction and the circumferential direction. The "thickness T10 of the shock absorption structure 10" in the present embodiment refers to the dimension in the radial direction from the inner peripheral surface to the outer peripheral surface of the shock absorption structure 10, rather than the outer diameter of the shock absorption structure 10. Note that the statement "the thickness T10 of the shock absorption structure 10 is constant in the axial direction" includes cases where the thickness T10 of the shock absorption structure 10 is slightly different in the axial direction within the range of manufacturing tolerances. Also, the statement "the thickness T10 of the shock absorption structure 10 is constant in the circumferential direction" includes cases where the thickness T10 of the shock absorption structure 10 is slightly different in the circumferential direction within the range of manufacturing tolerances. Note that in FIG. 4, the illustration of the second bracket 22 is omitted.

[0027] <Method for manufacturing a shock absorption structure> Next, the method for manufacturing the shock absorption structure of the present embodiment will be described. The method for manufacturing the shock absorption structure includes a cutting step of cutting a fabric and a composite step of composite-molding a matrix material onto the cut fabric.

[0028] The fabric has, for example, a plurality of warp threads and a plurality of weft threads, and the warp threads and the weft threads are intertwined with each other. The warp threads and the weft threads are made of reinforcing fibers such as carbon fibers. Note that the fabric may be one in which a warp thread layer in which a plurality of warp threads are arranged and a weft thread layer in which a plurality of weft threads are arranged are laminated, and the warp thread layer and the weft thread layer are bonded to each other by binding threads.

[0029] The thickness of the fabric is constant. Strictly speaking, the thickness of the fabric is thick at the part where the yarns overlap and thin at the part where the yarns do not overlap. Therefore, the fact that the thickness of the fabric is constant means that the thickness of the part where the yarns overlap is thinner than the upper limit value of the allowable thickness, and the thickness of the part where the yarns do not overlap is thicker than the lower limit value of the allowable thickness.

[0030] The matrix material is, for example, a thermosetting resin such as an epoxy resin, a vinyl ester resin, an unsaturated polyester resin, or a phenolic resin. As shown in FIG. 5, in the cutting step, the fabric 30 is cut into a desired cutting shape. The cutting shape of the fabric 30 is set to the shape obtained by developing the impact-absorbing structure 10 of the desired shape. In the present embodiment, the fabric 30 is cut into the cutting shape indicated by the two-dot chain line in FIG. 5. The cut fabric 30 has a first side 31, a second side 32, and a pair of third sides 33. The first side 31, the second side 32, and the pair of third sides 33 are each a plane along the thickness direction of the fabric 30. The first side 31 extends linearly. The length of the second side 32 is longer than the length of the first side 31. The second side 32 extends in an arc shape such that the distance from the first side 31 gradually increases from both ends toward the middle portion. The pair of third sides 33 connect the first side 31 and the second side 32. The third side 33 extends linearly. The distance between the pair of third sides 33 gradually increases from the first side 31 toward the second side 32.

[0031] The composite forming step of the present embodiment is performed using the RTM (Resin Transfer Molding) method. Specifically, the composite forming step includes a molding step, a filling step, a curing step, and a taking-out step.

[0032] The forming process is a process of forming the cut fabric 30 into a desired shape by a forming die (not shown). The forming die of the present embodiment has a conical middle die, and an upper die and a lower die sandwiching the middle die. The cut fabric 30 is wound around the middle die such that a pair of third sides 33 face each other. That is, the cut fabric 30 is formed into a cylindrical shape by being rolled up such that a pair of third sides 33 face each other. The upper die and the lower die sandwich the middle die around which the cut fabric 30 is wound. The filling process is a process of impregnating the thermosetting resin into the fabric 30 by filling the thermosetting resin into the forming die containing the fabric 30. The curing process is a process of curing the thermosetting resin in the forming die. Thereby, the fabric 30 and the thermosetting resin are combined to form a fiber-reinforced composite material. The taking-out process is a process of taking out the fiber-reinforced composite material from the forming die. The taken-out fiber-reinforced composite material is the impact-absorbing structure 10.

[0033] In the forming process, the cut fabric 30 is formed into a cylindrical shape by being rolled up such that a pair of third sides 33 face each other. Therefore, in the manufactured impact-absorbing structure 10, the first side 31 is located at the first end portion 10a of the impact-absorbing structure 10. The second side 32 is located at the second end portion 10b of the impact-absorbing structure 10. Further, in the cutting process, the first side 31 of the fabric 30 is cut so as to extend linearly. Therefore, the first side 31 becomes an inclined surface 11 that is inclined with respect to the plane P perpendicular to the axial direction at the first end portion 10a and the inclination angle θ with respect to the plane P gradually changes in the axial direction. Furthermore, the thickness of the fabric 30 becomes the thickness T10 of the impact-absorbing structure 10. Since the thickness of the fabric 30 is constant, the thickness T10 of the impact-absorbing structure 10 is constant in the axial direction.

[0034] <Test of Impact-Absorbing Structure> The inventor conducted tests on the relationship between the shape of the shock-absorbing structure and the shock load received by the shock-absorbing structure. The inventor prepared the shock-absorbing structures of Test Examples 1, 2, and 3. The shock-absorbing structures of Test Examples 1, 2, and 3 are plate-shaped shock-absorbing structures. In the shock-absorbing structures of Test Examples 1, 2, and 3, only the shape of the end portion in the extending direction is different. Hereinafter, the shape of the end portion of the shock-absorbing structures of Test Examples 1, 2, and 3 will be described in detail.

[0035] Figures 6 and 7 show the shock-absorbing structure 40 of Test Example 1. As shown in Figure 6, the end portion 40a of the shock-absorbing structure 40 has a pair of inclined surfaces 41 that are inclined with respect to the plane P perpendicular to the extending direction. The pair of inclined surfaces 41 are also both end surfaces of the end portion 40a of the shock-absorbing structure 40 in the width direction. The pair of inclined surfaces 41 are inclined so as to approach each other toward the tip. The inclination angle θ41 of the inclined surface 41 with respect to the plane P is constant in the extending direction. In other words, the inclination angle θ41 of the inclined surface 41 with respect to the plane P does not change in the extending direction.

[0036] As shown in Figure 7, the thickness T40 of the shock-absorbing structure 40 is constant in the extending direction. Note that the thickness T40 of the shock-absorbing structure 40 refers to the plate thickness of the shock-absorbing structure 40.

[0037] Figures 8 and 9 show the shock-absorbing structure 50 of Test Example 2. As shown in Figure 8, the end portion 50a of the shock-absorbing structure 50 has a pair of inclined surfaces 51 that are inclined with respect to the plane P perpendicular to the extending direction. The pair of inclined surfaces 51 are also both end surfaces of the end portion 50a of the shock-absorbing structure 50 in the width direction. The pair of inclined surfaces 51 are inclined so as to approach each other toward the tip. The inclination angle θ51 of the inclined surface 51 with respect to the plane P is constant in the extending direction. In other words, the inclination angle θ51 of the inclined surface 51 with respect to the plane P does not change in the extending direction. The inclination angle θ51 of the inclined surface 51 with respect to the plane P is the same as the inclination angle θ41 of the inclined surface 41 with respect to the plane P.

[0038] As shown in FIG. 9, the thickness T50 of the shock absorption structure 50 varies in the extending direction. Note that the thickness T50 of the shock absorption structure 50 refers to the plate thickness of the shock absorption structure 50. Specifically, the end portion 50a of the shock absorption structure 50 has a first portion 52 and a second portion 53 located on the tip side of the first portion 52. The plate thickness of the first portion 52 is thicker than the plate thickness of the second portion 53. The plate thickness of the second portion 53 gradually becomes thinner from the first portion 52 toward the tip. Therefore, the thickness T50 of the shock absorption structure 50 is constant at the first portion 52, but gradually becomes thinner toward the tip at the second portion 53.

[0039] FIGS. 10 and 11 show the shock absorption structure 60 of Test Example 3. As shown in FIG. 10, the end portion 60a of the shock absorption structure 60 has a pair of inclined surfaces 61 that are inclined with respect to a plane P perpendicular to the extending direction. The pair of inclined surfaces 61 are also both end surfaces of the end portion 60a of the shock absorption structure 60 in the width direction. The pair of inclined surfaces 61 are inclined so as to approach each other toward the tip. The inclination angle of the inclined surface 61 with respect to the plane P varies in the extending direction. Specifically, each of the pair of inclined surfaces 61 has a first surface 61a and a second surface 61b located on the tip side of the first surface 61a. The inclination angle θ61a of the first surface 61a with respect to the plane P is the same as each of the inclination angle θ41 of the inclined surface 41 with respect to the plane P and the inclination angle θ51 of the inclined surface 51 with respect to the plane P. The inclination angle θ61b of the second surface 61b with respect to the plane P is smaller than the inclination angle θ61a of the first surface 61a with respect to the plane P.

[0040] As shown in FIG. 10, the thickness T60 of the shock absorption structure 60 is constant in the extending direction. Note that the thickness T60 of the shock absorption structure 60 refers to the plate thickness of the shock absorption structure 60.

[0041] As described above, the shock-absorbing structure 50 of Test Example 2 is obtained by providing a starting point of deformation by thinning the thickness of the end portion of the shock-absorbing structure with respect to the shock-absorbing structure 40 of Test Example 1. The shock-absorbing structure 60 of Test Example 3 is obtained by providing a starting point of deformation by changing the inclination angle of the inclined surface with respect to the plane P with respect to the shock-absorbing structure 40 of Test Example 1. Then, the inventor applied an impact to the shock-absorbing structures 40, 50, and 60 until the lengths of the shock-absorbing structures 40, 50, and 60 in the extending direction deformed to a predetermined length.

[0042] FIG. 12 is a graph showing the test results of Test Example 1. FIG. 13 is a graph showing the test results of Test Example 2. FIG. 14 is a graph showing the test results of Test Example 3. The load on the vertical axis in FIGS. 12, 13, and 14 is the impact load received by the shock-absorbing structures 40, 50, and 60. The stroke amount on the horizontal axis is the amount of change in the length of the shock-absorbing structures 40, 50, and 60 in the extending direction. The amount of absorbed impact energy on the vertical axis is the amount of impact energy absorbed by the shock-absorbing structures 40, 50, and 60. The amount of absorbed impact energy corresponds to the integral value of the load and the stroke amount. Note that each scale line in the graph indicates the same value in FIGS. 12, 13, and 14.

[0043] As shown in FIG. 12, in Test Example 1, the load rapidly increases at the initial stage of deformation and then rapidly decreases. In the subsequent deformation process, the load fluctuates near the decreased value. Also, the maximum value of the load at the initial stage of deformation is larger than the average value of the load in the subsequent deformation process. That is, in Test Example 1, the fluctuation range of the load is large. Therefore, it can be said that the shock-absorbing structure 40 of Test Example 1 does not receive the impact load stably. In particular, when the maximum value of the load at the initial stage of deformation is larger than the average value of the load in the subsequent deformation process, the vehicle will decelerate rapidly during a collision, so the passengers in the vehicle are likely to be impacted.

[0044] As shown in Fig. 13, in Test Example 2, the load increases at the initial stage of deformation and then, without decreasing rapidly, fluctuates near the increased value. That is, in Test Example 2, the fluctuation range of the load is smaller than that in Test Example 1. Therefore, it can be said that the shock-absorbing structure 50 in Test Example 2 receives the impact load more stably than the shock-absorbing structure 40 in Test Example 1. This is because in Test Example 2, by reducing the thickness T50 of the shock-absorbing structure 50, a starting point of deformation is provided at the end 50a of the shock-absorbing structure 50.

[0045] On the other hand, the slope of the load at the initial stage of deformation in Test Example 2 is smaller than that at the initial stage of deformation in Test Example 1. That is, in Test Example 2, the load increases gently at the initial stage of deformation compared with Test Example 1. As a result, the amount of absorbed shock energy when the shock-absorbing structure 50 in Test Example 2 is deformed to a predetermined length is smaller than the amount of absorbed shock energy when the shock-absorbing structure 40 in Test Example 1 is deformed to a predetermined length. This is because in Test Example 2, by reducing the thickness T50 of the shock-absorbing structure 50, the cross-sectional area perpendicular to the extending direction, that is, the area of the surface receiving the impact load, becomes smaller.

[0046] As shown in Fig. 14, in Test Example 3, similar to Test Example 1, the load increases rapidly at the initial stage of deformation and then decreases. In the subsequent deformation process, the load fluctuates near the value when it increased at the initial stage of deformation. The difference between the maximum value of the load at the initial stage of deformation in Test Example 3 and the average value of the load in the subsequent deformation process is smaller than the difference between the maximum value of the load at the initial stage of deformation in Test Example 1 and the average value of the load in the subsequent deformation process. That is, in Test Example 3, the fluctuation range of the load is smaller than that in Test Example 1. Therefore, it can be said that the shock-absorbing structure 60 in Test Example 3 receives the impact load more stably than the shock-absorbing structure 40 in Test Example 1. This is because in Test Example 3, by changing the inclination angle of the inclined surface 61 with respect to the plane P in the extending direction, a starting point of deformation is provided at the end 60a of the shock-absorbing structure 60.

[0047] Also, the slope of the load at the initial stage of deformation in Test Example 3 is almost the same as the slope of the load at the initial stage of deformation in Test Example 1. As a result, the amount of impact energy absorbed when the impact absorption structure 60 of Test Example 3 is deformed to a predetermined length is almost the same as the amount of impact energy absorbed when the impact absorption structure 40 of Test Example 1 is deformed to a predetermined length. This is because the thickness T60 of the impact absorption structure 60 in Test Example 3 is constant in the extending direction. Thereby, as in Test Example 2, it is suppressed that the cross section perpendicular to the extending direction, that is, the area of the surface receiving the impact load becomes small.

[0048] In addition, in the above test, the shapes of the impact absorption structures 40, 50, and 60 were plate-like, but it has been confirmed that even if the shape of the impact absorption structure 10 is cylindrical as in the present embodiment, the tendency of the test results does not change. That is, when a starting point of deformation is provided in the impact absorption structure 10 by changing the inclination angle θ of the inclined surface 11 with respect to the plane P perpendicular to the extending direction in the extending direction, the impact absorption structure 10 can stably receive an impact load. Further, when the thickness T10 of the impact absorption structure 10 is constant in the extending direction, it is possible to avoid a decrease in the amount of impact energy absorbed by the impact absorption structure 10.

[0049] [Operations and Effects of the Present Embodiment] The operations and effects of the present embodiment will be described. (1) The first end portion 10a of the shock absorption structure 10 has an inclined surface 11 that is inclined with respect to a plane P perpendicular to the extending direction. For this reason, the shock absorption structure 10 can be deformed in order from the first end portion 10a by the first end portion 10a serving as a starting point of deformation. Further, the thickness T10 of the shock absorption structure 10 is constant in the extending direction. That is, a starting point of deformation is provided in the shock absorption structure 10 without reducing the thickness T10 of the shock absorption structure 10. For this reason, it is possible to suppress a decrease in the area of a cross section perpendicular to the extending direction of the shock absorption structure 10, that is, the area of a surface that receives an impact load, as in the prior art. Therefore, the impact load received by the shock absorption structure 10 at the time of a collision rapidly increases. Thus, the shock absorption structure 10 can stably receive the impact load without reducing the amount of absorbed shock energy.

[0050] Furthermore, the inclination angle θ of the inclined surface 11 with respect to the plane P perpendicular to the extending direction changes in the extending direction. Thereby, the maximum value of the impact load received by the shock absorption structure 10 at the initial stage of deformation approaches the average value of the impact load received by the shock absorption structure 10 in the subsequent deformation process as compared with the case where the inclination angle θ of the inclined surface 11 with respect to the plane P perpendicular to the extending direction does not change. Thus, a rapid deceleration of the vehicle at the time of a collision is suppressed. As a result, the impact received by the vehicle occupant at the time of a collision can be reduced.

[0051] (2) The inclination angle θ of the inclined surface 11 with respect to the plane P perpendicular to the extending direction gradually changes in the extending direction. Thereby, the impact received by the vehicle occupant at the time of a collision can be further reduced.

[0052] (3) The method for manufacturing the shock absorption structure 10 includes a cutting step of cutting a fabric 30 having a constant thickness, and a forming step of forming the fabric 30 cut in the cutting step into a cylindrical shape by rounding. In the cutting step, the fabric 30 is cut into a shape having a first side 31 extending linearly, a second side 32 longer than the first side 31, and a pair of third sides 33 connecting the first side 31 and the second side 32. In the forming step, the cut fabric 30 is rounded so that the pair of third sides 33 face each other.

[0053] In the cutting process, the first side 31 of the fabric 30 is cut so as to extend linearly, and in the forming process, the cut fabric 30 is formed into a cylindrical shape with a pair of third sides 33 facing each other. Therefore, the first side 31 becomes an inclined surface 11 that inclines with respect to the plane P perpendicular to the axial direction at the first end portion 10a of the shock-absorbing structure 10, and the inclination angle θ with respect to the plane P gradually changes in the axial direction. Further, the thickness of the fabric 30 becomes the thickness T10 of the shock-absorbing structure 10. Since the thickness of the fabric 30 is constant, the thickness T10 of the shock-absorbing structure 10 is constant in the axial direction.

[0054] In the method for manufacturing the shock-absorbing structure of the present embodiment, by devising the cutting shape of the fabric 30, the inclined surface 11 can be provided at the first end portion 10a of the shock-absorbing structure 10 only by rounding the cut fabric 30 and forming it into a cylindrical shape. In this case, processing such as cutting the first end portion 10a in order to provide a starting point of deformation at the first end portion 10a of the shock-absorbing structure 10 is unnecessary. Therefore, the productivity of the shock-absorbing structure 10 is improved, and the material yield of the shock-absorbing structure 10 is improved.

[0055] (4) The diameter of the shock-absorbing structure 10 increases from the first end portion 10a toward the second end portion 10b in the extending direction. For this reason, the area of the cross section perpendicular to the extending direction of the shock-absorbing structure 10 increases from the first end portion 10a toward the second end portion 10b. Therefore, the shock-absorbing structure 10 can receive the impact load more stably.

[0056] [Modification Example] In addition, each of the above embodiments can be modified as follows. Each of the above embodiments and the following modification examples can be implemented in combination with each other within a technically non-conflicting range.

[0057] ○ The shock-absorbing structure 10 does not have to be cylindrical. The shock-absorbing structure 10 may be, for example, polygonal cylindrical, or may be plate-shaped like the shock-absorbing structure 60 in Test Example 3.

[0058] ○ The cross-sectional shape of the shock absorption structure 10 does not have to be a closed cross-sectional shape such as the circular shape of the above-described embodiment. The cross-sectional shape of the shock absorption structure 10 may be an open cross-sectional shape such as a C shape or a hat shape, for example.

[0059] ○ If the inclination angle θ of the inclined surface 11 with respect to the plane P perpendicular to the extending direction changes in the extending direction, it does not have to change gradually. For example, as shown in FIG. 15, the inclined surface 11 may be composed of a first surface 11c and a second surface 11d having different inclination angles with respect to the plane P. The second surface 11d is located on the tip side of the first surface 11c in the extending direction. The inclination angle θd of the second surface 11d with respect to the plane P is smaller than the inclination angle θc of the first surface 11c with respect to the plane P. That is, the inclination angle θ of the inclined surface 11 with respect to the plane P perpendicular to the extending direction changes in two steps in the extending direction. In this case, compared with the case where the inclination angle θd of the second surface 11d with respect to the plane P is larger than the inclination angle θc of the first surface 11c with respect to the plane P, the area of the cross section perpendicular to the extending direction in the second surface 11d can be increased. Therefore, the amount of absorbed shock energy can be increased.

[0060] For example, as shown in FIG. 16, the inclined surface 11 may be composed of a first surface 11e and a second surface 11f having different inclination angles with respect to the plane P. The second surface 11f is located on the tip side of the first surface 11e in the extending direction. The inclination angle θf of the second surface 11f with respect to the plane P is larger than the inclination angle θe of the first surface 11e with respect to the plane P. That is, the inclination angle θ of the inclined surface 11 with respect to the plane P perpendicular to the extending direction changes in two steps in the extending direction.

[0061] Note that the inclined surface 11 may be composed of three or more surfaces having different inclination angles with respect to the plane P. That is, the inclination angle θ of the inclined surface 11 with respect to the plane P perpendicular to the extending direction may change in multiple steps of three steps or more in the extending direction.

[0062] ○ The diameter of the shock-absorbing structure 10 may be constant in the extending direction. Note that "the diameter of the shock-absorbing structure 10 is constant in the extending direction" includes the case where the diameter of the shock-absorbing structure 10 slightly varies within the range of manufacturing tolerance in the extending direction.

[0063] ○ The manufacturing method of the shock-absorbing structure is not limited to the method of the above embodiment. For example, the shock-absorbing structure 10 may be manufactured by injection molding. Specifically, after melting a thermosetting resin containing reinforcing fibers, it is poured into a mold having a cavity of a desired shape. Then, the thermosetting resin is cured within the mold. Thereby, the shock-absorbing structure 10 made of a fiber-reinforced composite material is formed.

[0064] ○ The shock-absorbing structure 10 may be provided at the rear or side of the vehicle. When the shock-absorbing structure 10 is provided at the rear of the vehicle, the shock-absorbing structure 10 may be provided so as to support the rear bumper with respect to the rear end portion of the rear side member. Also in this case, the extending direction of the shock-absorbing structure 10 is the front-rear direction.

[0065] When the shock-absorbing structure 10 is provided at the side of the vehicle, the extending direction of the shock-absorbing structure 10 is preferably the left-right direction. That is, the extending direction of the shock-absorbing structure 10 is set based on the direction of the impact load assumed from the position where it is provided on the vehicle.

[0066] ○ The shock-absorbing structure 10 may be provided outside the vehicle.

Explanation of Reference Numerals

[0067] 10... shock-absorbing structure, 10a... first end as an end, 11... inclined surface, 11c... first surface, 11d... second surface, 30... fabric, 31... first side, 32... second side, 33... third side, P... plane.

Claims

1. An impact absorption structure extending in a predetermined extending direction, wherein the impact absorption structure is made of a fiber reinforced composite material in which a fabric rounded into a cylindrical shape and a resin are combined, an end portion in the extending direction has an inclined surface inclined with respect to a plane perpendicular to the extending direction, the inclined surface has a first end and a second end which are ends of the inclined surface at an end in the width direction of the impact absorption structure, the second end is located on the tip side with respect to the first end, an inclination angle of the inclined surface with respect to the plane changes in the extending direction, and a thickness of the impact absorption structure is constant in the extending direction. An impact absorption structure characterized by this.

2. The impact absorption structure according to claim 1, wherein an inclination angle of the inclined surface with respect to the plane gradually changes in the extending direction.

3. The inclined surface has a first surface and a second surface located on the tip side of the first surface in the extending direction, and an inclination angle of the second surface with respect to the plane is smaller than an inclination angle of the first surface with respect to the plane. The impact absorption structure according to claim 1.

4. A method for manufacturing an impact absorption structure having a cylindrical shape that expands in diameter in the axial direction and is made of a fiber reinforced composite material in which a fabric and a resin are combined, a cutting step of cutting the fabric having a constant thickness, and a forming step of forming the fabric cut in the cutting step into a cylindrical shape by rounding, and a filling step of impregnating the resin into the fabric rounded into a cylindrical shape. In the cutting step, the fabric is cut into a shape having a first side extending linearly, a second side longer than the first side, and a pair of third sides connecting the first side and the second side, and in the forming step, the cut fabric is rounded so that the pair of third sides face each other. A method for manufacturing an impact absorption structure characterized by this.

5. An impact absorption structure extending in a predetermined extending direction, wherein an end portion in the extending direction has an inclined surface inclined with respect to a plane perpendicular to the extending direction, an inclination angle of the inclined surface with respect to the plane changes in the extending direction, a thickness of the impact absorption structure is constant in the extending direction, and the inclined surface has a first surface and a second surface located on the tip side of the first surface in the extending direction. ​ The impact-absorbing structure is characterized in that the inclination angle of the second surface with respect to the plane is smaller than the inclination angle of the first surface with respect to the plane.

Images