JP2012131442A - Impact absorbing member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impact absorbing member which has superior impact absorption characteristics.SOLUTION: According to the impact absorbing member, overlapping portions of a small-diameter pipe 4 and a large-diameter pipe 5 are subjected to a pipe-expanding process or pipe-contracting process to form radially projecting the overlapping projections 41 and 51, via which both pipes 4 and 5 are connected together. Out of both pipes 4 and 5, the pipe 5 located in the direction of projection of the overlapping projections 41 and 51 is treated as a deformable pipe while the other pipe 4 is treated as a non-deformable pipe. When impact is applied to both pipes 4 and 5 to compress them along their axial direction, the overlapping projection 41 of the non-deformable pipe 4 causes the peripheral wall of the deformable pipe 5 to deform plastically in the radial direction as the small-diameter pipe 4 is press fitted into the large-diameter pipe 5, thereby absorbs impact energy. In such an impact absorbing member, a representative taper angle θin an action area A2 of the overlapping projections 41 and 51 is set to 3.5° to 12.5°.

Description

  The present invention relates to an impact absorbing member used as, for example, a crash box of a bumper beam for an automobile and related technology.

 Inside the bumper provided at the front end of the automobile, a bumper beam is provided to absorb the impact at the time of collision.

  The bumper beam includes a bumper reinforcement arranged along the vehicle width direction and a pair of left and right crash boxes that support the bumper reinforcement on the vehicle structure, and absorbs collision energy by compressive deformation of the crash box. Yes.

  As such a shock absorbing crash box, those disclosed in Patent Documents 1 and 2 are well known.

  This crush box is integrally provided with a small-diameter pipe part that constitutes one half, a large-diameter pipe part that constitutes the other half, and a step part that connects both pipes. While the plastic pipe is continuously deformed so as to be squeezed into the small diameter pipe portion, the small diameter pipe portion is immersed in the large diameter pipe portion to absorb the collision energy.

Japanese Patent No. 4436620 Special table 2007-503561

  By the way, the crash box as the impact absorbing member is compressed and deformed in the axial direction (vehicle longitudinal direction) to absorb the collision energy, and therefore, the impact energy is absorbed by the crash box when the compression deformation is completed. After that, the impact is directly applied to the vehicle structure. Therefore, the maximum value of the compression displacement amount of the crash box is the effective stroke length. Conventionally, various studies and experiments have been conducted so that sufficient impact energy can be absorbed within the range of the effective stroke length, that is, shock absorption characteristics can be improved.

  FIG. 11 is a graph (load-displacement diagram) showing the relationship between the load and the amount of displacement when a general automobile crash box is compressed and deformed in the axial direction. A value obtained by integrating this diagram within the range of the effective stroke length S1 is an energy amount (actual EA amount) absorbed by the crash box. Therefore, the impact absorption characteristic can be improved by increasing the amount of EA.

  In order to increase the amount of EA within the effective stroke length S1, the following conditions (1) to (3) are important.

  (1) The maximum load is as large as possible without exceeding the breaking load of the vehicle structure.

  (2) The initial load L1 rises quickly. That is, the initial load L1 is recognized when the amount of displacement is as small as possible.

  (3) Regardless of the amount of displacement, there is little variation in the load, and the load approximates the maximum load as much as possible within the entire range of the effective stroke length S1.

  FIG. 12 is an ideal load-displacement diagram satisfying the above conditions (1) to (3). A value obtained by integrating this line segment within the range of the effective stroke length S1 is an ideal EA amount.

  Therefore, it can be said that the higher the ratio of the actual EA amount to the ideal EA amount, the more efficiently the impact energy can be absorbed and the more excellent shock absorption characteristics.

  However, conventionally, in the technical field of impact absorbing members such as a crash box for a vehicle, the variation in the load is large within the range of the effective stroke length, and the load greatly varies depending on the amount of displacement. As described above, the above condition (3) cannot be sufficiently satisfied, and there is a problem that it is difficult to further improve the shock absorption characteristics.

  This invention is made | formed in view of said subject, and it aims at providing the impact-absorbing member which can improve an impact-absorbing characteristic, and its related technique.

  In order to solve the above problems, the present invention comprises the following means.

[1] With the end of the small-diameter pipe inserted into the end of the large-diameter pipe, the overlapped portion of both pipes is expanded or contracted, and the overlapped convex portion protruding in the outer diameter direction or the inner diameter direction By being formed, both the tubes are connected, and among the two tubes, the tube arranged on the protruding direction side of the overlapping convex portion is a deformed tube, and the remaining one tube is a non-deformed tube. When an impact that compresses along the axial direction is applied, the peripheral wall of the deformed tube is plastically deformed in the outer diameter direction or the inner diameter direction by the overlapping convex portion of the non-deformed tube, while the small diameter tube An impact absorbing member adapted to absorb impact energy by being press-fitted into a pipe,
The direction in which the non-deformable tube moves relative to the deformed tube at the time of shock absorption is the rear, the opposite direction is the front,
In a side cross-sectional view when cut along a plane including the axis, a region where the overlapping convex portions of the non-deformed tube and the deforming tube are in contact with each other is defined as a overlapping convex portion contact region, and in the overlapping convex portion contact region The position where the amount of protrusion in the outer diameter direction or the inner diameter direction is the maximum as the deformation start point, the rear end position of the overlapping convex contact area as the deformation end point,
Of the overlapping convex contact area, an area between the deformation start point and the deformation end point is an action area, and the length of the action area in the axial direction is used as a reference from the deformation start point on the action area. A position moved 20% rearward along the axial direction is defined as a first representative point, and a position moved 20% forward along the axial direction from the deformation end point is defined as a second representative point.
The shock absorption, wherein the representative taper angle is set to 3.5 ° to 12.5 ° when the angle with respect to the axis of the straight line connecting the first and second representative points is a representative taper angle. Element.

  [2] The impact absorbing member according to [1], wherein at least a part of the working region of the overlapping convex portion of the non-deformable tube is formed into a linear tapered portion in a side sectional view.

[3] The superposition convex part is constituted by an outward convex part projecting in the outer diameter direction,
3. The preceding item 1 or 2, wherein when the shock is absorbed, the outer convex portion of the small-diameter pipe is plastically deformed so that a peripheral wall of the large-diameter pipe forming the deformed pipe is expanded in the outer radial direction. Shock absorbing member.

[4] The superposition convex part is constituted by an inward convex part protruding in the inner diameter direction,
3. The impact absorption according to item 1 or 2, wherein the inward convex portion of the large-diameter pipe is plastically deformed so that a peripheral wall of the small-diameter pipe forming the deformed pipe is pushed in an inner diameter direction when the shock is absorbed. Element.

  [5] The impact-absorbing member according to any one of [1] to [4], wherein the overlapping convex portion is formed in a whole area in a circumferential direction of the small-diameter pipe and the large-diameter pipe.

  [6] The impact absorbing member according to any one of [1] to [4], wherein the overlapping convex portion is formed on a part of a circumferential direction of the small diameter tube and the large diameter tube.

[7] A method for producing the impact-absorbing member according to any one of items 1 to 6,
A method for producing an impact absorbing member, wherein the superposed convex portions are formed by performing pipe expansion processing or contraction processing using a mold on the superposed portions of the small diameter pipe and the large diameter pipe. .

[8] A crash box for a vehicle that supports the bumper reinforcement on the vehicle structure,
It is comprised by the impact-absorbing member according to any one of items 1 to 6,
A crash box for a vehicle, wherein the collision energy applied to the bumper reinforcement is absorbed.

[9] Bumper reinforcements arranged along the vehicle width direction;
A crash box for supporting the bumper reinforcement on the vehicle structure,
The crash box is configured by the shock absorbing member according to any one of the preceding items 1 to 6,
A bumper beam characterized in that collision energy applied to the bumper reinforcement is absorbed by the crash box.

  According to the impact absorbing member of the invention [1], since the gently sloping portion is formed in the action region of the overlapping convex portion of the non-deformable tube, the peripheral wall of the deformable tube can be applied to the axial center collision load. Can be preferentially and smoothly deformed in the radial direction rather than in the axial direction. Therefore, while reducing the initial load, the load can be approximated to the initial maximum load as much as possible over the entire effective stroke length, and sufficient impact energy can be absorbed smoothly, improving the shock absorption characteristics. Can do.

  According to the shock absorbing member of the invention [2], the taper portion having a linear cross section is formed in the action region of the overlapping convex portion of the non-deformable tube, so that the shock absorbing characteristics can be improved more reliably.

  According to the impact absorbing member of the inventions [3] and [4], the impact absorbing characteristics can be improved more reliably.

  According to the impact absorbing member of the invention [5], the amount of collision energy absorbed can be increased.

  According to the impact absorbing member of the invention [6], it is possible to easily adjust the amount of collision energy absorbed.

  According to the method for producing an impact absorbing member of the invention [7], an impact absorbing member having the above-described effects can be obtained with certainty.

  According to the crash box for a vehicle of the invention [8], the impact absorption characteristics can be improved as described above.

  According to the bumper beam of the invention [9], it is possible to improve the impact absorption characteristics as described above.

FIG. 1 is a plan view showing an automobile bumper beam to which a crash box according to a first embodiment of the present invention is applied. FIG. 2 is a perspective view showing a crush box in the pan bar beam of the first embodiment. FIG. 3 is a side sectional view showing the crash box of the first embodiment. FIG. 4 is a front view showing the crash box of the first embodiment. 5 is an enlarged side cross-sectional view of a portion surrounded by a one-dot chain line in FIG. FIG. 6A is a side cross-sectional view showing a tube expansion mold set in a crush box before tube expansion processing according to the first embodiment. FIG. 6B is a side sectional view showing the crush box of the first embodiment in a state immediately after the tube expansion process. FIG. 7 is a perspective view showing a crash box according to a second embodiment of the present invention. FIG. 8 is a side cross-sectional view showing an enlarged main part of the crash box of the second embodiment. FIG. 9 is a perspective view showing a crash box which is a modification of the present invention. FIG. 10A is a load-displacement diagram in the crash box of Example 1 of the present invention. FIG. 10B is a load-displacement diagram in the crash box according to the second embodiment of the present invention. FIG. 10C is a load-displacement diagram in the crush box according to the third embodiment of the present invention. FIG. 10D is a load-displacement diagram in the crash box according to the fourth embodiment of the present invention. 10E is a load-displacement diagram in the crash box of Comparative Example 1. FIG. 10F is a load-displacement diagram in the crush box of Comparative Example 2. FIG. FIG. 11 is a load-displacement diagram of a general automobile crash box. FIG. 11 is an ideal load-displacement diagram of a car crash box.

<First Embodiment>
FIG. 1 is a plan view showing an automobile bumper beam to which a crash box according to a first embodiment of the present invention is applied.

  As shown in the figure, a bumper beam 1 for an automobile according to the first embodiment includes a bumper reinforcement 2 disposed along the vehicle width direction at the front end of the automobile, and tip ends on both sides of the bumper reinforcement 2. Crash boxes 3 and 3 that are fixed in a state where the portion (front end portion) penetrates.

  The base end portions (rear end portions) of the crash boxes 3 and 3 are fixed to a pair of side members (side frames) (not shown) as vehicle structures via bumper stays 7 and 7, so that the bumper The beam 1 is assembled to the vehicle body.

  As shown in FIGS. 2 to 4, the crash box 3 functions as an impact absorbing member. The crush box 3 includes a small-diameter tube 4 disposed on the front side (front end side) and a large-diameter tube 5 disposed on the rear side (base end side) and separate from the small-diameter tube 4.

  The small-diameter pipe 4 and the large-diameter pipe 5 are made of, for example, an extruded shape material or a drawn shape material made of aluminum or an alloy thereof.

  However, in the present invention, the material of the small diameter tube 4 and the large diameter tube 5 is not limited, and copper or an alloy thereof, iron or an alloy thereof, or the like may be used as the material.

  Both the small diameter pipe 4 and the large diameter pipe 5 have a circular cross section. The small-diameter pipe 4 has a smaller diameter than the large-diameter pipe 5 and is slightly smaller in size. The small-diameter pipe 4 can be inserted into the large-diameter pipe 5 while aligning the axis of each other. It is configured.

  In addition, in a state where the rear end portion (base end portion) of the small-diameter tube 4 is inserted into the front end portion (tip end portion) of the large-diameter tube 5, a required portion of the overlapping portion (overlapping portion) of both the tubes 4 and 5. However, it is expanded (expanded). As a result, outward convex portions 41 and 51 as superposed convex portions projecting in the outer diameter direction are formed in the overlapping portion, and the outward convex portion 41 on the small diameter tube 4 side becomes the outward convex portion on the outer diameter tube 5 side. The small-diameter pipe 4 is fastened and fixed to the large-diameter pipe 5 by press-contacting with the inner peripheral surface of the portion 51.

  In the first embodiment, the outward projecting portions 41 and 51 are continuous in the circumferential direction of the small diameter tube 4 and the large diameter tube 5 and are formed over the entire circumference.

  In the first embodiment, of the small-diameter pipe 4 and the large-diameter pipe 5, the large-diameter pipe 5 is on the protruding direction (outer diameter direction of the pipes 4 and 5) side of the outward convex parts (overlapping convex parts) 41 and 51. Therefore, the large-diameter pipe 5 is configured as a deformed pipe, and the small-diameter pipe 4 is arranged on the side of the outward projections 41 and 51 in the anti-projection direction (inner diameter direction of the pipes 4 and 5). The small-diameter pipe 4 is configured as a non-deformable pipe that forms the remaining one pipe. Therefore, as will be described later, the strength (deformation yield strength) of the small diameter tube 4 is greater than the strength (deformation yield strength) of the large diameter tube 5 so that the peripheral wall of the large diameter tube 5 can be deformed by the outward convex portion 41 of the small diameter tube 4. Is also strongly formed. Specifically, the small diameter pipe 4 is thicker than the large diameter pipe 5.

  Here, in the present invention, the non-deformable tube is not a tube that does not deform at all during shock absorption, but may be a tube that deforms within a range in which a predetermined shock absorption characteristic can be secured. Specifically, the non-deformable tube only needs to have a deformation amount that is smaller than that of the deformation tube when absorbing the shock. Needless to say, in the present invention, the non-deformed tube includes a tube that does not deform at all when absorbing an impact.

  Moreover, in this invention, a deformation | transformation pipe | tube deform | transforms by absorption of impact energy and does not deform | transform at the time of normal use.

  In the present embodiment, the configuration of the outward projections 41 and 51 is particularly characteristic. Therefore, the detailed configuration of the outward projections 41 and 51 will be described below with reference to the enlarged sectional view of the main part of FIG. However, it will be explained.

  In the following description, the side sectional view of FIG. 5, that is, the sectional view when cut along a plane including the axial center will be described. Further, the direction in which the non-deformable tube (small-diameter tube) 4 moves relative to the deformable tube (large-diameter tube) 5 relative to the deformable tube (large-diameter tube) 5 at the time of shock absorption, which will be described later, is the rear, and vice versa The direction (left direction in the figure) is assumed to be the front.

  First, a region where the outward convex portions 41 and 51 of the small-diameter pipe 4 and the large-diameter tube 5 are in contact with or in pressure contact with each other is referred to as a superposed convex portion contact region (superimposed convex portion press-contact region) A1. Furthermore, the position where the protrusion amount in the outer diameter direction in the overlapping convex contact area A1 is the maximum is defined as a deformation start point P1, and the rear end position of the overlapping convex area contact area A1 is defined as a deformation end point P2.

  Moreover, let the area | region between the deformation | transformation start point P1 and the deformation | transformation end point P2 among superposition | polymerization convex part contact area | region A1 be the action area | region A2. Further, when the length of the action area A2 in the axial direction is used as a reference, that is, when the length is 100%, the position moved 20% rearward along the axis direction from the deformation starting point P1 on the action area A2. Is a first representative point Q1, and a position that is moved 20% forward along the axial direction from the deformation end point P2 on the action area A2 is a second representative point Q2.

  The straight line passing through the first representative point Q1 and the second representative point Q2 is a representative straight line T, and the angle of the representative straight line T with respect to the straight line X in the axial direction, that is, the angle of the representative straight line T with respect to the axial center is represented as a representative taper angle θ. To do.

  In the first embodiment, it is necessary to set the representative taper angle θ to 3.5 ° to 12.5 °, and more preferably to set to 3.5 ° to 10 °.

  That is, when the representative taper angle θ is set within the specific range, the ratio of the actual EA amount to the ideal EA amount (vs. ideal EA value) is high, as will be apparent from the following examples. Thus, excellent shock absorption characteristics can be obtained. In other words, when the representative taper angle θ is too large, the anti-ideal EA value becomes small, which makes it difficult to obtain good shock absorption characteristics, which is not preferable. Moreover, when the representative taper angle θ is too small, the length of the crash box 3 becomes very long, which is not preferable as an energy absorbing member.

  In the crash box 3 of the first embodiment, the portion corresponding to the portion between the first and second representative points Q1, Q2 in the outward convex portion 41 of the small-diameter tube 4 is formed in a straight line in a side sectional view. The taper portion 45 is configured.

  In the first embodiment, the outward projecting portions 41 and 51 are formed at a time by tube expansion using a tube expansion die (expanding die).

  That is, as shown in FIGS. 6A and 6B, the tube expansion die 6 used in the first embodiment includes a split die 61 that is inserted through the overlapping portion of both tubes 4 and 5. The split mold 61 includes a plurality of mold segments (die segments) divided in the circumferential direction, and is formed in a substantially cylindrical shape corresponding to the inner peripheral shape of the small diameter tube 4. 6A and 6B, the alternate long and short dash line indicates the center line (axial center).

  On the outer peripheral surface of the split mold 61, a pressing convex portion 62 is formed corresponding to a position where the outward convex portions 41 and 51 in both the pipes 3 and 4 are to be formed. Needless to say, the outer peripheral surface shape of the pressing convex portion 62 is formed corresponding to the inner peripheral surface shape of the outward convex portions 41 and 51.

  Further, the split mold 61 is provided with a wedge insertion portion 63 along the axial direction. The inner peripheral surface of the wedge insertion part 63 is formed in a conical shape or a polygonal pyramid shape.

  The mandrel 65 for expanding the tube expansion mold 6 is provided with a wedge 66 corresponding to the wedge insertion portion 63 of the split mold 61. The wedge 66 has a tapered tip, and an outer peripheral surface shape corresponding to the inner peripheral surface shape of the wedge insertion portion 63 is formed in a conical shape or a polygonal pyramid shape. The taper angle of the outer peripheral surface of the wedge 66 is set to be equal to the taper angle of the inner peripheral surface of the wedge insertion portion 63.

  When the wedge 66 of the mandrel 65 is inserted into the wedge insertion portion 63 of the split mold 61 in the tube expansion die 6, each mold segment of the split mold 61 is pushed by the wedge 66 in the outer radial direction, and the outer radial direction It is supposed to be displaced.

  In order to form the outward convex portions 41 and 51 on the small-diameter tube 4 and the large-diameter tube 5 using the tube expansion die 6, as shown in FIG. 6A, the proximal end portion of the small-diameter tube 4 before the convex portion is formed. Is placed in a state of being fitted (freely fitted) to the tip of the large-diameter pipe 5. Subsequently, the split mold 61 is inserted and disposed in both the tubes 4 and 5, and the pressing convex portion 62 of the split mold 61 is disposed in the projected portion formation planned portion in the overlapping portion of the both tubes 4 and 5.

  In this state, as shown in FIG. 6B, the wedge 66 is forcibly inserted into the wedge insertion portion 63 by pressing the mandrel 65 along the axis. Thereby, each type | mold segment of the split type 61 is displaced to an outer-diameter direction, and the convex part formation scheduled part in both the pipes 4 and 5 is pipe-expanded.

  By this tube expansion processing, as described above, the convex portions to be formed on both the tubes 4 and 5 are locally expanded in the outer diameter direction, and the outward projections projecting to the both tubes 4 and 5 in the outer diameter direction. 41 and 51 are formed. As a result, the outer peripheral surface of the outward convex portion 41 on the small diameter tube 4 side is pressed into engagement with the inner peripheral surface of the outward convex portion 51 of the large diameter tube 5, and the small diameter tube 4 is fastened and fixed to the large diameter tube 5. The

  In this embodiment, a push type tube expansion method for pushing the mandrel into the split mold is used. However, the present invention is not limited to this, and in the present invention, a pull type tube expansion method for drawing the mandrel is used. Can also be adopted. And the outward convex parts 41 and 51 can be formed accurately and reliably by using the pipe expansion process using a metal mold | die like this embodiment.

  As shown in FIG. 1, the bumper reinforcement 2 is constituted by an extrusion mold material, a plate material, a drawing mold material, or the like made of aluminum or an alloy thereof, a plate press product made of a steel material, or the like.

  The bumper reinforcement 2 is formed in a hollow shape such as a square (rectangular) cross section. In order to improve the strength and the like, a reinforcing wall such as a partition wall may be formed in the hollow portion of the bumper reinforcement 2.

  Further, the bumper reinforcement 2 is formed so that the intermediate portion slightly protrudes forward by bending the both side portions in the vehicle width direction rearward in a plan view.

  And the front part (front-end | tip part) of the small diameter pipe | tube 4 in the two crush boxes 3 is fixed in the state penetrated by the front-back direction at the both-ends part of the bumper reinforcement 2. FIG.

  As this fixing method, a tube expansion method similar to the above can be used. For example, the expanded pipe portions 48 that protrude in the outer diameter direction and are continuous in the circumferential direction are formed on both the front and rear sides of the through-hole portion of the bumper reinforcement 2 in the small diameter pipe 4 by the same pipe expansion processing as described above. The small diameter tube 4 of the crush box 2 is connected and fixed to the bumper reinforcement 2 by press-engaging the expanded portion 48 with the peripheral edge of the through portion of the bumper reinforcement 2.

  In the present embodiment, the operation of attaching the small-diameter pipe 4 to the bumper reinforcement 2 (formation work of the expanded pipe portion 48), and the connection of the small-diameter pipe 4 and the large-diameter pipe 5 (formation work of the outward convex portions 41 and 51) Can be performed simultaneously. In this case, productivity can be improved.

  Needless to say, the method of fixing the crash box 3 to the bumper reinforcement 2 is not limited to tube expansion processing, and other fixing means such as welding or bolting may be used.

  Thus, the crash box 3 is attached to the bumper reinforcement 2 and the bumper beam 1 is assembled.

  Further, the bumper beam 1 is assembled to the vehicle structure via bumper stays 7 and 7.

  That is, the bumper stay 7 is formed of a molded product made of aluminum or an alloy thereof.

  Then, the rear end portion (base end portion) of the large-diameter pipe 5 of the crash box 3 is fixed in a state where the rear end portion (base end portion) of the crash box 3 is disposed through the central portion of the bumper stay 7.

  As this fixing method, the same tube expansion method as described above can be used. For example, the expanded pipe portions 58 that protrude in the outer diameter direction and are continuous in the circumferential direction are formed on both the front and rear sides of the through-hole portion of the bumper stay 7 in the large diameter pipe 5 by pipe expansion processing. Then, the bumper stay 7 is assembled to the crash box 3 by press-engaging the expanded portion 58 with the peripheral edge of the penetrating portion of the pan bar stay 7.

  The work of assembling the crash box 3 to the bumper stay 7 may be performed simultaneously with the work of connecting the small diameter pipe 4 and the large diameter pipe 5 and the work of assembling the crash box 3 to the bumper reinforcement 2. . In this case, productivity can be improved.

  Note that the method of fixing the crash box 3 to the bumper stay 7 is not limited to the tube expansion process, and other fixing means such as welding or bolting may be used.

  In order to assemble the bumper beam 1 to which the bumper stays 7 and 7 are attached to the vehicle, the bumper stays 7 and 7 are fixed to the front end portion of the side member (side frame) of the vehicle by fixing means such as bolting or welding. To do.

  Thus, the bumper beam 1 is assembled to the vehicle to form an automobile impact absorbing device.

  In this bumper beam 1, when an impact (load) is applied in a direction in which the crash box 3 is compressed in the axial direction due to a collision with the bumper reinforcement 2 in the initial state shown in FIGS. However, it is press-fitted into the large-diameter pipe 5 while plastically deforming (expanding deformation) so as to push the peripheral wall of the large-diameter pipe 5 in the outer diameter direction by the outward convex portion 41, and the diameter is expanded at that time. The collision energy is absorbed by the deformation.

  As described above, according to the bumper beam 1 of the first embodiment, the peripheral wall of the large diameter tube 5 is continuously expanded and deformed by the outward convex portion 41 of the small diameter tube 4 in the crash box 3. The load due to the diameter expansion deformation is small and almost constant regardless of the amount of displacement in the axial direction, and the difference from the maximum load is small. For this reason, the ratio of the actual EA amount with respect to the ideal EA amount becomes high, and the impact absorption characteristics can be improved.

  Moreover, in the crash box 3 of the first embodiment, the maximum load (initial load) at the initial stage of deformation is based on deformation in the diameter expansion direction of the large diameter pipe 5 by the outward convex portion 41 of the small diameter pipe 4. The initial load is reduced, the difference from the subsequent load is also reduced, the collision energy can be absorbed smoothly immediately after the collision, and the impact absorption characteristics can be further improved.

  Furthermore, according to the crash box 3 of the present embodiment, since the representative taper angle θ is set in the specific range, the action region A1 involved in the plastic deformation in the outward convex portion 41 of the small-diameter pipe 4 is increased. It is formed in a sloping part that gently slopes. For this reason, when the shock is absorbed, the peripheral wall of the large-diameter pipe 5 is enlarged and deformed by the gentle inclined portion, so that the peripheral wall of the large-diameter pipe 5 is also more than in the axial direction against a collision load in the axial direction. It can be preferentially deformed in the outer diameter direction. In particular, in the first embodiment, since the taper portion 45 having a linear cross section is formed in the action region A2 of the outward convex portion 41 of the small-diameter pipe 4, the taper portion 45 has a large diameter when absorbing the shock. The peripheral wall of the pipe 5 can be smoothly deformed in the outer diameter direction. Therefore, while reducing the initial maximum load, the load can be approximated to the maximum load as much as possible over the entire effective stroke length, and sufficient impact energy can be absorbed smoothly, further improving the shock absorption characteristics. Can be improved.

  Moreover, since the amount of energy absorption can be easily adjusted simply by changing the height of the outward projecting portion 41 and changing the deformation amount of the peripheral wall of the large diameter pipe 5 in the diameter increasing direction, Accordingly, the load level can be easily adjusted, and excellent versatility can be obtained.

  In the first embodiment, the outward projecting portions 41 and 51 of the crash box 3 are formed continuously in the circumferential direction and over the entire circumference. However, the present invention is not limited to this, and in the present invention, FIG. As shown in FIG. 4, the crush box 3 may be formed with a plurality of overlapping convex portions 41, 51 at predetermined intervals in the circumferential direction, or partially overlapped in the circumferential direction of the crush box 3. May be formed.

  Thus, the energy absorption amount can also be adjusted by changing the circumferential length of the overlapping convex portion, and the load level can also be easily adjusted in this respect.

Second Embodiment
FIG. 7 is a perspective view showing a crash box according to a second embodiment of the present invention, and FIG. 8 is an enlarged side sectional view showing a main part of the crash box.

  As shown in these drawings, the crush box 3 of the second embodiment is different from the crush box 3 of the first embodiment in that the small diameter tube 4 and the large diameter tube 5 are superposed in the first embodiment. On the other hand, outward convex portions 41 and 51 are formed as overlapping convex portions, whereas in this second embodiment, inwardly protruding portions 42, 52 is formed.

  In other words, a required portion of the overlapped portion of the small diameter tube 4 and the large diameter tube 5 is subjected to contraction processing using a contraction mold. Thereby, inward convex portions 42 and 52 as superposed convex portions that protrude in the inner diameter direction and are continuous over the entire circumference in the circumferential direction are formed in the overlapping portion. The small-diameter pipe 4 is fastened and fixed to the large-diameter pipe 5 by press-engaging the inward-convex portion 52 on the large-diameter pipe 5 side with the inner peripheral surface of the inward-convex portion 42 on the small-diameter pipe 4 side.

  In the second embodiment, among the small diameter pipe 4 and the large diameter pipe 5, the small diameter pipe 4 is disposed on the protruding direction (inner diameter direction of the pipes 4, 5) side of the inward convex portions 42, 52. Since the small-diameter pipe 4 is configured as a deformed pipe and the large-diameter pipe 5 is disposed on the side of the inward projecting portions 42 and 52 in the anti-projection direction (outer diameter direction of the pipes 4 and 5), this large diameter The tube 5 is configured as a non-deformed tube forming the remaining one tube. Accordingly, the large-diameter pipe 5 is thicker than the small-diameter pipe 4 so that the peripheral wall of the small-diameter pipe 4 can be deformed by the inward convex portion 52 of the outer-diameter pipe 5. The (deformation strength) is formed stronger than that of the small diameter tube 4.

  Also in the crash box 3 of the second embodiment, as will be described in detail below, as in the first embodiment, a portion that plastically deforms the peripheral wall of the small-diameter tube 4 in the inward convex portion 52 of the large-diameter tube 5. In addition, a linear section (taper portion 55) is formed, and the representative taper angle θ is set within a predetermined range.

  Also in the second embodiment, the direction in which the non-deformable tube (large-diameter tube) 5 moves relative to the deformable tube (small-diameter tube) 4 relative to the deformable tube (small-diameter tube) 4 during shock absorption, that is, the left in FIG. A direction is assumed to be the rear, and the opposite direction (the right direction in the figure) is assumed to be the front. Therefore, in the crash box 3 of the second embodiment, the front-rear direction is opposite to the crash box 3 of the first embodiment shown in FIG.

  First, a region where the inward convex portions 42 and 52 of the small-diameter pipe 4 and the large-diameter tube 5 are in contact with or in pressure contact with each other is defined as a superposed convex portion contact region (superimposed convex portion press-contact region) A1. Furthermore, the position where the protruding amount in the inner diameter direction in the overlapping convex contact area A1 is the maximum is defined as a deformation start point P1, and the rear end position of the overlapping convex area contact area A1 is defined as a deformation end point P2.

  In addition, a region between the deformation start point P1 and the deformation end point P2 in the overlapping convex contact area A1 is defined as an action region A2. Further, a position where the length of the action area A2 in the axial direction is set as a reference, that is, the length is set to 100%, and the position moved 20% rearward along the axis direction from the deformation start point P1 on the action area A2 is the first. The representative point Q1 is defined as a second representative point Q2 that is 20% forwardly moved along the axial direction from the deformation end point P2 on the action area A2.

  The straight line passing through the first representative point Q1 and the second representative point Q2 is a representative straight line T, and the angle of the representative straight line T with respect to the straight line X parallel to the axis, that is, the angle of the representative straight line T with respect to the axis is the representative taper angle θ. And

  And in this 2nd Embodiment, it is necessary to set typical taper angle (theta) to 3.5 degrees-12.5 degrees similarly to the said 1st Embodiment, More preferably, it is 3.5 degrees-10 degrees. It is good to set to °.

  In the crash box 3 according to the second embodiment, as described above, the first and second representative points Q1 and Q2 of the inward convex portion 52 of the large-diameter pipe 5 are linearly viewed in a side sectional view. A tapered portion 55 is formed.

  In the second embodiment, the other configurations are substantially the same as those in the first embodiment, and thus the same reference numerals are given to the same parts or corresponding parts, and redundant description is omitted.

  In the crash box 3 of the second embodiment, when a load in a direction of compression along the axial direction is applied at the time of a collision, the peripheral wall of the small diameter tube 4 is moved in the inner diameter direction by the inward convex portion 52 of the large diameter tube 5. The small-diameter pipe 4 is press-fitted into the large-diameter pipe 5 while being plastically deformed (diameter-deformed) so as to be pushed. The collision energy is absorbed by the diameter reduction deformation at that time.

  Also in the crash box 3 of the second embodiment, the peripheral wall of the small-diameter pipe 4 is continuously reduced in diameter by the inward convex portion 52 of the large-diameter pipe 5 as in the first embodiment. Regardless of the amount of displacement in the direction of the heart, the load is small and almost constant, the difference from the maximum load is small, and the shock absorption characteristics can be improved.

  Moreover, in this crash box 3 as well, the maximum load (initial load) at the initial stage of deformation is based on the deformation in the reduced diameter direction of the small-diameter pipe 4 by the inward convex portion 52 of the large-diameter pipe 5. It becomes smaller and the difference from the subsequent load becomes smaller, so that the collision energy can be absorbed smoothly immediately after the collision, and the shock absorption characteristics can be further improved.

  Further, in the crash box 3 as well, since the representative taper angle θ is set in the above specific range, a gently inclined slope portion is formed in the action area A2 of the inward convex portion 52 of the large diameter pipe 5. The For this reason, when the shock is absorbed, the peripheral wall of the small-diameter tube 4 is expanded and deformed by the gentle inclined portion. Can be preferentially deformed. In particular, in the second embodiment, since the taper portion 55 having a linear cross section is formed in the action region A2 of the inward convex portion 51 of the large-diameter tube 5, the small diameter is reduced by the taper portion 55 during shock absorption. The peripheral wall of the tube 4 can be smoothly deformed in the inner diameter direction. Therefore, while reducing the initial maximum load, the load can be approximated to the maximum load as much as possible over the entire effective stroke length, and sufficient impact energy can be absorbed smoothly, further improving the shock absorption characteristics. Can be improved.

  Also in the second embodiment, the amount of energy absorption can be easily adjusted simply by changing the height of the inward convex portion 52 and changing the amount of deformation of the peripheral wall of the small-diameter pipe 4 in the direction of diameter reduction. Can do.

  Also in the second embodiment, as in the first embodiment, the inward convex portions 42 and 52 are not necessarily formed over the entire circumference, and may be partially formed in the circumferential direction. And the energy absorption amount can be adjusted similarly to the said 1st Embodiment by changing the length of the circumferential direction of the inward convex parts 42 and 52. FIG.

<Other variations>
In the above embodiment, the small-diameter tube 4 and the large-diameter tube 5 are circular in cross section, but the cross-sectional shape of the small-diameter tube and the large-diameter tube is not particularly limited, and is a polygonal shape such as a quadrangle, Small diameter pipes and large diameter pipes having an elliptical shape, an oval shape, or an irregular cross-sectional shape may be used. Furthermore, it is not necessary to form the small-diameter pipe and the large-diameter pipe in a similar shape. If the small-diameter pipe can be inserted into the large-diameter pipe, the small-diameter pipe and the large-diameter pipe should be formed in different cross-sectional shapes. Also good.

  Moreover, in the said embodiment, although the linear part (taper part 45, 55) by sectional view is formed in the action | operation area | region in the superposition convex part by the side of a deformation | transformation pipe | tube, it is not restricted only to it, In this invention, It is not always necessary to form a straight section in the working area of the superposed convex portion. For example, the entire working area of the overlapping convex portion may be formed in a curved shape such as an arc shape or an S shape in a cross-sectional view.

  Furthermore, in the present invention, when a linear taper portion is formed in the working region of the overlapping convex portion, all portions between the first and second representative points in the overlapping convex portion on the non-deformable tube side are not necessarily formed linearly. There is no need to do this, and it is only necessary to form a part of the working area of the superposed convex portion in a straight line.

  In the above embodiment, the case where the crash box as the shock absorbing member of the present invention is applied to the bumper beam of the bumper provided at the front end of the automobile has been described as an example. However, the present invention is not limited to this. The shock absorbing member can be applied to a crash box for a front underrun protector of a large vehicle, and further to a crash box for protecting a pedestrian or a crew member.

  The impact absorbing member of the present invention can also be used for a bumper beam provided at the rear end of an automobile. When provided at the rear end, needless to say, the distal end side is the rear side, and the proximal end side is the front side.

  In the above embodiment, the non-deformed tube is thicker than the deformed tube so as to be stronger than the deformed tube. However, the present invention is not limited to this, and in the present invention, the thickness is the same. However, the strength difference may be given by making the material of one tube and the other tube different between the small diameter tube and the large diameter tube. For example, one pipe is made of copper, the other pipe is made of aluminum, one pipe is made of iron, the other pipe is made of aluminum, one pipe is made of copper, and the other pipe is made of iron. You may make it give an intensity | strength difference. Moreover, even if it is the same material, you may make it give an intensity | strength difference to both pipes by changing a processing method.

  Hereinafter, examples related to the present invention and comparative examples that depart from the gist of the present invention will be described.

<Example 1>
The base end of an aluminum alloy small-diameter tube (non-deformed tube) 4 having a wall thickness of 2.0 mm and an outer diameter of φ66 mm is located within the distal end of an aluminum alloy large-diameter tube (deformed tube) 5 having a wall thickness of 1.5 mm and an inner diameter of φ67 mm. The outer convex portions (overlapping convex portions) 41 and 51 having a pipe expanding amount (protruding amount) of 1.0 mm are formed over the entire circumference by pipe expansion processing in the overlapped portion (overlapping portion). By fastening 4 and 5, the crash box 3 similar to that of the first embodiment was formed. The effective stroke length of the crash box 3 was set to 40 mm.

  In this case, as in the first embodiment, the portion between the representative points Q1 and Q2 of the outward projecting portion 41 of the small-diameter tube 4 is linearly formed in the side cross-sectional view to form the tapered portion 45. Further, the representative taper angle θ was set to 3.5 °.

  And about this crash box 3, the relationship (load-displacement diagram) of the load at the time of the collision load which compresses and deforms in an axial direction and the displacement amount was calculated | required. The result is shown in FIG. 10A.

  Also, based on the load-displacement diagram, the actual energy amount absorbed by the crash box of Example 1 (actual EA amount) and the ideal energy amount that can be absorbed to the maximum by the crash box of Example 1 (ideal) EA amount). Then, an ideal EA value represented by a ratio of the actual EA amount to the ideal EA amount (actual EA amount / ideal EA amount) was obtained as a percentage. The results are shown in Table 1.

  As shown in Table 1, it can be seen that the crash box of Example 1 has a very high anti-ideal EA value of 92.1% and very excellent shock absorption characteristics.

<Example 2>
As shown in Table 1, a crash box was produced in the same manner as in Example 1 except that the representative taper angle θ was set to 5.0 °. Then, for this crash box, a load-displacement diagram was obtained as shown in FIG. 10B, and an anti-ideal EA value was obtained as shown in Table 1. Also in this crash box, the anti-ideal EA value is as high as 94.8%, and it can be seen that the shock absorption characteristics are very excellent.

<Example 3>
As shown in Table 1, a crash box was produced in the same manner as in Example 1 except that the representative taper angle θ was set to 10.0 °. Then, for this crash box, a load-displacement diagram was obtained as shown in FIG. 10C and Table 1, and an anti-ideal EA value was obtained. Also in this crash box, the anti-ideal EA value is as very high as 90.0%, and it can be seen that the shock absorption characteristics are very excellent.

<Example 4>
As shown in Table 1, a crash box was produced in the same manner as in Example 1 except that the representative taper angle θ was set to 12.5 °. Then, for this crash box, as shown in FIG. 10D and Table 1, a load-displacement diagram was obtained, and an anti-ideal EA value was obtained. Also in this crash box, the anti-ideal EA value is as high as 83.3%, and it can be seen that the shock absorption characteristics are excellent.

<Comparative Example 1>
As shown in Table 1, a crash box was produced in the same manner as in Example 1 except that the representative taper angle θ was set to 15.0 °. Then, for this crash box, as shown in FIG. 10E and Table 1, a load-displacement diagram was obtained, and an anti-ideal EA value was obtained. In this crash box, the ideal EA value is as low as 78.8%, and it can be seen that the shock absorption characteristics are inferior.

<Comparative example 2>
Two arc lines are connected to the action area A2 of the outward convex portion 41 of the small-diameter tube 4 so that a section (tapered portion) having a linear cross section is not formed. A crush box was produced in the same manner as in Example 1 except that the tube-expansion process was performed on the overlap portion of the small-diameter pipe 4 and the large-diameter pipe 5 so that the S-shaped curve was formed. As shown in Table 1, the representative taper angle θ was 20.0 °.

  Then, as shown in FIG. 10F and Table 1, a load-displacement diagram was obtained for this crash box, and an anti-ideal EA value was obtained. This crash box has a low anti-ideal EA value of 77.9%, indicating that the shock absorption characteristics are inferior.

<Evaluation>
As apparent from Table 1 and FIGS. 10A to 10F, a taper portion 45 having a linear cross section is formed in the action region A2 of the outward convex portion 41 of the small diameter tube 4, and the representative taper angle θ is “3. The crash boxes of Examples 1 to 4 of “5 °”, “5.0 °”, “10.0 °”, and “12.5 °” have the representative taper angle θ as large as 15.0 °. Compared with the crash box of Comparative Example 2 which does not have a taper portion having a linear cross section in the action area A2 and has a very large representative taper angle θ of 20.0 °, the anti-ideal EA value is higher and the impact Excellent absorption characteristics.

  In particular, the crash box with the representative taper angle θ of “3.5 °”, “5.0 °”, and “10.0 °” has a very high anti-ideal EA value of over 90%, and has a shock absorbing characteristic. It was very good.

  As is clear from the above evaluation results, the crash box in which the representative taper angle θ is set to 3.5 ° to 12.5 °, more preferably 3.5 ° to 10 °, has excellent shock absorption characteristics. I understand that.

  Furthermore, it can be seen that when the tapered portion having a linear cross section is formed in the action region 4 of the outward convex portion 41 of the small-diameter tube 4, the shock absorption characteristics are further improved.

  The shock absorbing member of the present invention can be applied to a bumper beam crash box for automobiles.

1: Bumper beam 2: Bumper reinforcement 3: Crash box (shock absorbing member)
4: Small-diameter tube 41: outward convex portion (overlapping convex portion)
42: Inward convex portion (overlapping convex portion)
45: Taper part 5: Large diameter pipe 51: Outward convex part (polymerization convex part)
52: Inward convex portion (overlapping convex portion)
55: Taper part 6: Tube expansion die A1: Overlapping convex contact area A2: Action area P1: Deformation start point P2: Deformation end point Q1: First representative point Q2: Second representative point θ: Representative taper angle

Claims (9)

With the end of the small-diameter pipe inserted into the end of the large-diameter pipe, the overlapping portion of both pipes is expanded or contracted to form an overlapping convex portion protruding in the outer diameter direction or the inner diameter direction. As a result, both pipes are connected, and of these pipes, the pipe arranged on the protruding direction side of the overlapping convex part is a deformed pipe, the remaining one pipe is a non-deformed pipe, and both pipes are axially oriented. When the impact compressing is applied, the small-diameter pipe is press-fitted into the large-diameter pipe while the peripheral wall of the deformable pipe is plastically deformed in the outer diameter direction or the inner-diameter direction by the overlapping convex portion of the non-deformable pipe. A shock absorbing member adapted to absorb impact energy by being
The direction in which the non-deformable tube moves relative to the deformed tube at the time of shock absorption is the rear, the opposite direction is the front,
In a side cross-sectional view when cut along a plane including the axis, a region where the overlapping convex portions of the non-deformed tube and the deforming tube are in contact with each other is defined as a overlapping convex portion contact region, and in the overlapping convex portion contact region The position where the amount of protrusion in the outer diameter direction or the inner diameter direction is the maximum as the deformation start point, the rear end position of the overlapping convex contact area as the deformation end point,
Of the overlapping convex contact area, an area between the deformation start point and the deformation end point is an action area, and the length of the action area in the axial direction is used as a reference from the deformation start point on the action area. A position moved 20% rearward along the axial direction is defined as a first representative point, and a position moved 20% forward along the axial direction from the deformation end point is defined as a second representative point.
The shock absorption, wherein the representative taper angle is set to 3.5 ° to 12.5 ° when the angle with respect to the axis of the straight line connecting the first and second representative points is a representative taper angle. Element.   The impact absorbing member according to claim 1, wherein at least a part of the working region of the overlapping convex portion of the non-deformable tube is formed into a linear tapered portion in a side sectional view. The overlapping convex portion is constituted by an outward convex portion protruding in the outer diameter direction,
3. The plastic deformation according to claim 1, wherein when the shock is absorbed, the outer convex portion of the small-diameter pipe is plastically deformed so that a peripheral wall of the large-diameter pipe forming the deformed pipe is expanded in the outer radial direction. Shock absorbing member. The overlapping convex portion is constituted by an inward convex portion protruding in the inner diameter direction,
The impact according to claim 1 or 2, wherein, when absorbing the impact, the inward convex portion of the large-diameter pipe is plastically deformed so that a peripheral wall of the small-diameter pipe forming the deformable pipe is pushed in an inner diameter direction. Absorbing member.   The impact-absorbing member according to any one of claims 1 to 4, wherein the overlapping convex portion is formed in the entire area in the circumferential direction of the small-diameter pipe and the large-diameter pipe.   The impact-absorbing member according to any one of claims 1 to 4, wherein the overlapping convex portion is formed on a part of a circumferential direction of the small-diameter pipe and the large-diameter pipe. A method for producing the impact absorbing member according to any one of claims 1 to 6,
A method for producing an impact absorbing member, wherein the superposed convex portions are formed by performing pipe expansion processing or contraction processing using a mold on the superposed portions of the small diameter pipe and the large diameter pipe. . A vehicle crash box that supports a bumper reinforcement on a vehicle structure,
It is comprised by the impact-absorbing member of any one of Claims 1-6,
A crash box for a vehicle, wherein the collision energy applied to the bumper reinforcement is absorbed. Bumper reinforcements arranged along the vehicle width direction,
A crash box for supporting the bumper reinforcement on the vehicle structure,
The crash box is constituted by the impact absorbing member according to any one of claims 1 to 6,
A bumper beam characterized in that collision energy applied to the bumper reinforcement is absorbed by the crash box.

Images