JP5126503B2 - Crash box and its mounting structure - Google Patents

Description

  The present invention relates to a crash box and a structure for mounting the crash box on a vehicle body. Specifically, the invention is continuously stable even when an impact load due to a collision from an oblique direction as well as a direction parallel to the axial direction is input. Accordingly, the present invention relates to a crash box having an excellent shock absorption characteristic against an oblique collision, that is, a high shock absorption energy absorption amount, and a mounting structure thereof to a vehicle body.

  The body of an automobile generally has a monocoque structure in which strength members made of a cylindrical body such as a front side member, a side sill, and a rear side member are arranged at important points in the front-rear direction of the vehicle body. And in the case of a collision accident, the safety | security of a passenger | crew is aimed at by absorbing the impact energy loaded by a collision using these intensity | strength members as an impact-absorbing member.

  In recent years, a crash box is used as one of the shock absorbing members. For example, the crash box consists of a cylinder with a closed cross-sectional shape that is generally about 80 to 300 mm in total length, and is attached to the front end of the front side member and the rear end of the rear side member while supporting the bumper reinforcement. Can be installed freely. Usually, two crash boxes are arranged in the front-rear direction of the vehicle body, one for each bumper reinforcement.

  Crash boxes are impacted by impacts input to the bumper reinforcement at the time of a collision, giving priority to the front side members and rear side members that make up the body shell, and plastic buckling deformation and collapsing. This prevents damage to the body shell and reduces repair costs during light collisions, and effectively absorbs impact energy in cooperation with side members to protect passengers.

  Crash boxes that are cylindrical bodies are, for example, welded to two components, which are half-finished products formed by pressing thin steel plates, hydroformed to hollow pipes, and further to aluminum alloy materials It is manufactured into a predetermined shape by performing hot extrusion or cold extrusion.

  Many proposals have been made so far in order to improve the shock absorption characteristics of the crash box. For example, Patent Document 1 discloses an invention related to a crash box composed of a cylindrical body having a cross-shaped cross section having four branches of the same shape intersecting at right angles, and Patent Document 2 discloses an equiangular angle. An invention relating to a bumper beam including a crash box made of a hollow body having a cross section having four arms arranged is disclosed.

The present inventors disclosed a patented invention related to a crash box comprising a cylindrical body provided with a groove extending in the longitudinal direction on an outer wall excluding the ridge line portion, according to Patent Document 3. This crash box has improved shock absorption performance compared to the crash box disclosed in Patent Documents 1 and 2, and has priority over the front side member and rear side member due to the impact load applied in the axial direction. Then, the impact energy can be absorbed very efficiently by plastic buckling deformation and crushing in an accordion-like shape in substantially the entire axial direction.
EP0885681 Special table 2003-503272 gazette WO2005 / 010398

  In an actual automobile crash, the impact load due to the collision is continuously input in the axial direction of the crash box from the beginning to the beginning of the bellows-like plastic buckling deformation of the crash box. This is rather rare, and the input is often made obliquely with respect to the axial direction of the crash box.

FIG. 1 is an explanatory diagram schematically showing a so-called offset collision situation. Moreover, FIG. 2 is explanatory drawing which shows typically the input direction of the impact load to a crash box.
As indicated by arrows in FIG. 1, in the case of an off-off collision, an impact load is input in an oblique direction with respect to the longitudinal direction of the vehicle body 1. Also, in the case of a vehicle-to-vehicle collision accident, an impact load is input in an oblique direction with respect to the vehicle height direction due to a difference in bumper installation height of each vehicle. That is, as shown in FIG. 2, an impact load is input to the crash box 2 arranged so as to be directed in the front-rear direction of the vehicle body 1 from an oblique direction with respect to the vehicle width direction and / or the vehicle height direction. There are many cases.

  On the other hand, the crash box disclosed in Patent Document 3 certainly generates plastic buckling deformation in a bellows shape stably over almost the entire area in the axial direction against an impact load applied in the axial direction. However, if an impact load is input in an oblique direction with respect to the axial direction, a bending moment is generated in the cylindrical body, and this bending moment causes a point in the middle of the bellows-like plastic buckling deformation. In this case, large bending deformation is likely to occur in the entire cylinder. When such a large bending deformation occurs, it becomes difficult to perform a plastic buckling deformation in the shape of a bellows thereafter, so that the ability to absorb impact energy decreases accordingly.

The present invention includes a pair of corner portions disposed opposite to each other and another pair of corner portions disposed perpendicular to a line connecting the pair of corner portions, and has no flange on the outside. A crash box composed of a metal cylinder having a rectangular cross-sectional shape, wherein an angle formed by a pair of corner portions is 90 ° or more and 150 ° or less and an angle formed by another pair of corner portions is 30 The cross-sectional shape is symmetrical with respect to the line passing through the pair of corner portions, and the pair of sides that are symmetrically arranged with respect to the line passing through the pair of corner portions. One or a plurality of grooves that are provided in each of at least one pair of sides and that extend in the longitudinal direction and protrude toward the inside at positions excluding the pair of corner portions and the other pair of corner portions. With The thickness t (mm), the length W (mm) of the side, the number N of grooves, and the average value Wc (mm) of the opening widths of the N grooves in each of the sides are expressed by the following formula (1). And a radius of curvature of all the corner portions is larger than any of the plurality of corner portions constituting the groove .

5 <(W−N × Wc) / (N + 1) / t <50 (1)
In this case, it is desirable to satisfy the relationship of the following formula (1 ′).
5 <(W−N × Wc) / (N + 1) / t <30 (1 ′)
In these crash boxes according to the present invention, the grooves are provided on all four sides, or the plate thickness t (mm) and the side length W ( mm) preferably satisfies the relationship of the following formula (2).

5 <(W / t) <50 (2)
In these crash boxes according to the present invention, it is desirable that the angle formed by the pair of corner portions is larger than the angle formed by the other pair of corner portions.

  These crash boxes according to the present invention further include a notch portion in which a region including at least one corner portion is notched in a planar shape, and the thickness t (mm) and the length of the notch portion. It is desirable that the length W ′ (mm) satisfies the relationship of the following formula (3). However, the length W (mm) of the side in the above formula (1) means the length of the side in a state where the notch is provided.

5 <(W ′ / t) <50 (3)
In this case, it is more desirable to satisfy the relationship of the following formula (3 ′).

5 <(W ′ / t) <30 (3 ′)
These crash boxes according to the present invention further include a notch portion formed by cutting a region including at least one corner portion of the pair of corner portions and the other pair of corner portions into a flat shape, The length of the notch is 50 times or more the plate thickness of the cylindrical body, and extends in the longitudinal direction to a position excluding the corners at both ends of the notch and is convex toward the inside. The notch has a thickness t (mm), a length W ′ (mm), the number N of grooves, and an average value Wc (mm) of the opening widths of the N grooves. It is desirable to satisfy the relationship of Formula (4). However, in this case, the length W (mm) of the side in the above formula (1) means the length of the side in a state where the notch is provided.

5 <(W′−N × Wc) / (N + 1) / t <50 (4)
In this case, it is more desirable to satisfy the relationship of the following formula (4 ′).

5 <(W′−N × Wc) / (N + 1) / t <30 (4 ′)
Moreover, when providing a notch part, a cylindrical body is overlap | superposed and joined the edge part of one structural member, or the edge part of each of the some structural member divided | segmented along an axial direction is piled up. It is desirable that the cut-out portion is an overlapped joint portion of one constituent member or an overlapped joint portion of a plurality of constituent members.

The crash box according to these present invention, furthermore, it is desirable that the symmetrical shape to the line passing through the other pair of corner portions.

The present invention preferably includes a pair of corner portions disposed opposite to each other and another pair of corner portions disposed perpendicular to a line connecting the pair of corner portions, and has an outer flange. From a metal cylinder having a rectangular cross-sectional shape that does not have a cross-section and joined by overlapping the edges of each of the two components divided along the axial direction. A crash box configured, wherein an angle formed by the pair of corner portions and an angle formed by the other pair of corner portions are both 90 °, and the cross-sectional shape is a line passing through the pair of corner portions. , And any other line passing through the other pair of corner portions, and positions excluding the pair of corner portions and the other pair of corner portions on all four sides constituting the rectangular cross section Long The cutout portion has one or a plurality of grooves extending in the direction and projecting toward the inside, and a cutout portion formed by cutting a region including another pair of corner portions into a flat shape. but without the joint overlay each other a plurality of components, in each of all sides, the plate thickness t (mm), a side in a state that is provided to notch a length W (mm), the number of grooves N , and the average value Wc of the opening width of the N grooves (mm) is, satisfy the relationship of the following formula (1), the notch of the plate thickness t (mm) and length W '(mm), the following The crash box is characterized in that the relationship of the expression (3) is satisfied and the curvature radius R of all corner portions is larger than any curvature radius Rc of a plurality of corner portions constituting the groove .

5 <(W−N × Wc) / (N + 1) / t <50 (1)
5 <(W ′ / t) <50 (3 )

  From another viewpoint, the present invention is directed to the above-described crash box according to the present invention in the direction in which a line passing through a pair of corner portions is directed, or the direction in which a line passing through another pair of corner portions is directed. This is a structure for attaching a crash box to a vehicle body, which is characterized by being attached to the vehicle body in a vertical direction.

  According to the crash box and the mounting structure of the vehicle body according to the present invention, it is possible to suppress the occurrence of bending deformation as a whole even with respect to an impact load that is applied obliquely with respect to the axial direction. Since it is possible to generate a continuously stable bellows-like plastic buckling deformation, it is possible to ensure excellent shock absorption characteristics, that is, a high shock absorption energy absorption amount even against an oblique collision.

  As a result, damage to the body shell can be suppressed to reduce the repair cost during a light collision, and impact energy can be effectively absorbed to improve the safety of the passenger.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out a crash box and a mounting structure for a vehicle body according to the present invention will be described with reference to the accompanying drawings. First, the principle of the crash box according to the present invention will be described.
(1) Principle A polygonal cross-section, which is a cross-sectional shape of a crash box that is a cylinder, is composed of an angle that forms a ridge line part in the cylinder and a side that is a plane part between the ridge line parts in the cylinder. When a load is applied in the axial direction of this cylindrical body and a load acts on this cross section, the ridge line part and the flat part cause out-of-plane deformation (deformation toward the outside of the closed cross section), but the ridge line has high rigidity. The portion generates an out-of-plane deformation that is smaller than that of the plane portion whose rigidity is relatively low with respect to the ridgeline, and also generates a compressive strain. Thereafter, as the applied load increases, the amount of out-of-plane deformation also increases in the ridge line portion, eventually the ridge line portion buckles and the ridge line portion breaks, and plastic buckling deformation occurs. This crush box absorbs impact energy by repeating these series of deformations several times, and by plastic buckling deformation in a bellows shape in the axial direction and crushing.

  This series of deformation behavior changes depending on the direction of the input load. For example, when a load in the oblique direction with respect to the axial direction of the crash box is input, the amount of out-of-plane deformation of the ridge line portion is increased and the compressive strain is larger than when the load is input in the axial direction. Get smaller. Further, when the inputted oblique load is increased, the compressive strain generated in the ridge line portion is reduced as much as possible, a large out-of-plane deformation is generated, the ridge line portion is bent with a large curvature radius, and the entire crash box is bent. In particular, when the load input from an oblique direction acting on the flat surface portion having low rigidity is increased, the crash box is easily bent.

  For this reason, in order to suppress the bending of the entire crash box and improve the shock absorption performance against the impact load applied in the oblique direction with respect to the axial direction, the cross section of the crash box is based on the following viewpoints. It is effective to determine the shape.

That is, in order to be able to suppress bending deformation with respect to load input from an oblique direction,
(I) Increasing the degree of load of the oblique load in the ridge line portion having high rigidity, that is, a cross-sectional shape in which the ridge line portion is arranged with respect to the input direction of the oblique load, and (II) the ridge line portion is oblique It is important to reduce the out-of-plane deformation caused by the load input from the direction and to have a cross-sectional shape that increases the compressive strain.

  Further, when an impact load is input in the axial direction of the cylindrical body constituting the crash box, the cylindrical body undergoes a plurality of plastic buckling deformations, and the impact absorption energy is determined by the load history generated at that time. In other words, the amount of impact energy absorbed is determined by the number of plastic buckling deformations that occur continuously.

  First, when an impact load is input to the cylinder, the plane portion constituting the cross section of the cylinder undergoes out-of-plane deformation, and the ridge line portion causes compressive strain. After that, as the input impact load increases, the out-of-plane deformation at the plane portion and the compressive strain at the ridge line portion both increase, and eventually the out-of-plane deformation at the ridge line portion occurs. Buckling occurs n times (n is a natural number of 1 or more) at the ridge line portion. And the buckling wrinkle produced | generated by the buckling deformation which arose in the ridgeline part is expanded to a plane part, and a buckling wrinkle produces | generates in a plane part. Thereafter, the buckling wrinkles generated in this plane portion are overlapped, and the process proceeds to the next buckling deformation (n + 1) occurring in another part in the axial direction.

  The interval from the n-th buckling occurrence to the (n + 1) -th buckling occurrence, that is, the buckling wavelength, is affected by the size of the wrinkles generated by the buckling of the ridge portion of the deformation as described above. In addition, the size of the wrinkles is governed by out-of-plane deformation that occurs in the flat portion. Therefore, in order to improve the impact energy absorption performance by the plastic buckling behavior with a short buckling wavelength, it is effective to reduce the out-of-plane deformation that occurs in the plane portion.

That is, in order to obtain high impact energy absorption while suppressing bending deformation, in order to cause continuous plastic buckling deformation with a short buckling wavelength,
(III) It is important to shorten the length of the plane portion in order to control out-of-plane deformation to be small, and (IV) to provide a desired length of the short plane portion by providing a recess having a ridge line in the plane portion. It is.
(2) Crash box according to the present invention Next, based on this principle, the crash box according to the present invention will be described.

  FIG. 3 is an explanatory view showing the basic cross-sectional shape of the crash box 3 according to the present invention. 4 (a) to 4 (d) are explanatory views showing various cross-sectional shape examples of the crash boxes 3-1 to 3-4 according to the present invention.

  As shown in FIG. 3, the crash box 3 of the present invention includes a pair of corner portions 4 and 5 that are arranged to face each other, and another that is arranged orthogonal to a line connecting the pair of corner portions 4 and 5. And a pair of corner portions 6, 7 and a metal cylinder having a rectangular cross section defined by the corner portions 4 to 7 and having no flange on the outside.

  In order to stably generate the continuous plastic buckling deformation, it is required to continuously overlap the buckling wrinkles generated by the buckling deformation. In the case of a metal cylinder having a cross-sectional shape having a flange on the outer side, it is necessary to overlap the wrinkle in a direction different from that of the flat portion when the buckling wrinkle is also superimposed on the flange, and the deformation resistance at that time is increased. . In other words, a metal cylinder having a cross-sectional shape having a flange on the outside cannot easily be buckled and wrinkled. For the above reasons, the metal cylinder can stably exhibit plastic buckling deformation when it does not have a flange on the outer side in the cross-sectional shape. Therefore, the crash box 3 of the present invention is formed of a metal cylinder having a rectangular cross section defined by the corner portions 4 to 7 and having no flange on the outside.

  As described above, the crash box 3 includes a corner portion 4 that is a ridge line portion having a high rigidity that forms an outline of a cross-sectional shape in the vehicle width direction (left-right direction in FIG. 3) or the vehicle height direction (up-down direction in FIG. 3). It has a quadrangular cross-sectional shape in which ˜7 are arranged.

  The cross-sectional shape of the crash box 3 is symmetrical to a virtual line l passing through the pair of corner portions 4 and 5. Furthermore, it is desirable that the shape is symmetrical with respect to a line passing through the other pair of corner portions 6 and 7. This is because the higher the symmetry, the higher the performance against oblique loads from various input directions.

  In the case of an offset collision, an oblique load in the vehicle width direction or the vertical direction is input, so that a bending moment is generated in the crash box 3. In order for the crash box 3 to stably generate plastic buckling deformation even when the load is input from such an oblique direction, the entire bending deformation (bending) caused by the bending moment is suppressed, and the input It is important that the generated impact load causes continuous plastic buckling deformation with a short buckling wavelength similar to the case where the impact load is input in the axial direction of the cylindrical body. This is because when the bending deformation occurs in the entire cylindrical body, the deformation has a long buckling wavelength. Therefore, corner portions 6 and 7 having high rigidity are arranged at positions corresponding to the outer edges where the load acts. For this reason, in this crash box 3, as shown in FIG. 4A, the corner portions 6 and 7 are arranged on a straight line passing through the center of the cross section.

In the crash box 3, the internal angles θ ₁ and θ ₂ formed by the pair of corner portions 4 and 5 are set to 90 ° to 150 ° and the internal angles formed by the other pair of corner portions 6 and 7. θ ₃ and θ ₄ are set to 30 ° or more and 90 ° or less. The reason for this will be explained.

The rigidity of the corner portions 4 to 7 as the ridge line portion is determined by the arc length existing in the ridge line portion. When the corner portions 4 to 7 are set with a specific curvature radius, the arc length is set to the corner portions 4 to 7. Varies depending on the interior angle. Therefore, in order to cause plastic buckling deformation by the impact load without causing the entire bending of the crash box 3 with respect to the bending moment generated by the impact load input from an oblique direction, the pair of corner portions 4, The internal angles θ ₁ and θ ₂ formed by 5 are set to 90 ° to 150 °. When θ ₁ and θ ₂ exceed 150 °, the corner portion has a practical radius of curvature (approximately 1.5 to 10.0 mm) determined within a range that takes into account the manufacturing and design space of the crash box. The arc lengths 6 and 7 are too short to secure desired rigidity, and the targeted plastic buckling deformation cannot be generated.

Further, the angles θ ₃ and θ ₄ of the inner angles formed by the other pair of corner portions 6 and 7 are interlocked with the angles θ ₁ and θ ₂ of the inner angles formed by the pair of corner portions 4 and 5, so the angles θ ₁ and θ _{With 2} being 90 ° or more and 150 ° or less, 30 ° or more and 90 ° or less.

When higher bending rigidity is required for the other pair of corner portions 6 and 7 than the pair of corner portions 4 and 5, the angles θ ₁ and θ ₂ formed by the pair of corner portions 4 and 5 are different from each other. It is desirable that the angles θ ₃ and θ ₄ formed by the pair of corner portions 6 and 7 be larger.

  The crash box 3 has a shape capable of increasing the degree of load of the oblique load at the corner portions 4 to 7 that are ridge portions having high rigidity, that is, the corner portions 4 to 7 are arranged in the input direction of the oblique load. The cross-sectional shape is as follows. Moreover, by setting it as the cross-sectional shape which provides the corner parts 4-7, while being able to reduce the out-of-plane deformation | transformation which arises with respect to the load input from the diagonal direction, the compressive strain with respect to the corner parts 4-7 is raised. be able to.

  Further, the crash box 3 includes two pairs of sides (8, 9) and (10, 11) arranged symmetrically with respect to a virtual straight line 1 passing through the pair of corner portions 4 and 5. Each of the sides 8 and 9 forming a pair of at least one pair extends in the longitudinal direction and protrudes inward at a position excluding the pair of corner portions 4 and 5 and the other pair of corner portions 6 and 7. One or a plurality of grooves 12 and 13 (one case is shown in FIG. 3) are provided.

  These grooves 12 and 13 have a plate thickness t (mm), a length W (mm) of the sides 8 to 11, the number N of the grooves 12 and 13, and the N grooves 12 in the sides 8 and 9, respectively. 13, the average value Wc (mm) of the opening widths satisfies the relationship of the following equation (1), preferably the relationship of the following equation (1 ′).

5 <(W−N × Wc) / (N + 1) / t <50 (1)
5 <(W−N × Wc) / (N + 1) / t <30 (1 ′)
As a result, the crash box 3 can be plastic buckled and deformed in a bellows shape with a short buckling wavelength, and high impact absorption energy absorption performance can be obtained. The reason for this will be explained.

  From the occurrence of buckling to the next occurrence of buckling, the crash box 3 causes continuous plastic buckling (progressive buckling), and in order to increase the amount of shock absorption energy absorption determined by the load history caused by the deformation. It is effective to suppress the load fluctuation of the material, that is, to shorten the buckling wavelength. This buckling wavelength is closely related to the out-of-plane deformation (displacement) caused by the impact load in the cross section of the crash box 3, and if the amount of this out-of-plane deformation is large, the buckling wavelength becomes long. If is small, the buckling wavelength is short. Therefore, in order to reduce the out-of-plane deformation occurring in the cross section of the crash box 3, the width of the sides 8 to 11 constituting the cross section, that is, the distance between the adjacent corner portions 4 to 7 may be reduced.

  Specifically, the distance W between the corner portions 4 to 7 is set to be less than 50 times the plate thickness t of the cylinder. That is, in this crush box 3, the plate thickness t (mm) and the side length W (mm) at each of the sides 10 and 11 forming a pair with no grooves 12 and 13 are expressed by the following formula (2). Satisfy the relationship.

5 <(W / t) <50 (2)
On the other hand, on the sides 8 and 9 where the distance W between the corner portions 4 to 7 is 50 times or more the plate thickness t, as shown in FIG. 8 and 9 are divided, and the sides 8 and 9 excluding the grooves 12 and 13 satisfy the relationship of the above expression (2).

  Even if the distance W between the corner portions 4 to 7 is less than 50 times the plate thickness, the flat portions 8 and 9 are further divided by providing the flat portions 8 and 9 with the grooves 12 and 13. You may do it.

  It is desirable to provide the grooves 8 and 9 at positions that do not include the corner portions 4 to 7 that become the starting point of plastic buckling deformation due to the suppression of the overall bending deformation when an oblique load is applied.

  As described above, the crush box 3 is provided with the grooves 12 and 13 in the flat portions 8 and 9 in order to obtain a short buckling wavelength when the width W of the flat portions 8 and 9 is large. A new ridge line portion is formed by the grooves 12 and 13, and the widths of the plane portions 8 and 9 are controlled within a range in which a short buckling wavelength can be obtained.

  Here, in order to surely obtain the above-described effect, the plate thickness t (mm), the length W (mm) of the sides 8 to 11 and the number N of the grooves 12 and 13 in all the sides 8 to 11, It is desirable that the average value Wc (mm) of the opening widths of the N grooves 12 and 13 satisfies the relationship of the formula (1): 5 <(W−N × Wc) / (N + 1) / t <50. (2): It is desirable to satisfy the relationship of 5 <(W−N × Wc) / (N + 1) / t <30.

Incidentally, when the depth _{d c} of the groove 12, 13 is too shallow, since the weakened effect of cutting edges 8 and 9 described above, the depth _{d c} of the groove 12, 13 is preferably set to 10mm greater.
In the crash box 3, it is desirable that the curvature radius R of all the corner portions 4 to 7 is larger than any curvature radius Rc of the corner portions 14 to 21 constituting the grooves 12 and 13. The reason for this will be explained.

  The cross-sectional secondary moment of the thin-walled ring is governed by the diameter and the wall thickness, and the cross-sectional secondary moment increases as the diameter increases, and the section modulus that affects the bending strength also increases as the diameter increases. That is, in order to suppress bending deformation against a bending moment generated when a load is applied to the crash box 3 from an oblique direction, the corner portions 4 to 4 that are positioned on the outer surface of the cross section and support the input load. It is effective to increase the second moment of section 7. Moreover, when the curvature radius of the corner | angular parts 14-21 which comprise the groove | channels 12 and 13 is enlarged, the deformation resistance in the groove | channels 12 and 13 will increase too much, and it will become difficult to produce the plastic buckling deformation in this part.

  For the reasons described above, in the present invention, the radius of curvature R of all the corner portions 4 to 7 that dominate the overall bending strength of the crash box 3 is set to the radius of curvature Rc of the corner portions 14 to 21 constituting the grooves 12 and 13. It is desirable to make it larger.

Thus, the crash boxes 3 of the present embodiment, the corner portion 4-7 disposed in the vehicle width direction or the vehicle height direction, the optimum range interior angle theta ₁ through? ₄ which form the corner portion 4-7 And at least one set of two pairs of sides (8, 9) and (10, 11) that are symmetrically arranged on a virtual straight line l passing through the pair of corners 4 and 5 By providing one or a plurality of grooves that extend in the longitudinal direction at positions other than the corners 4, 6, and 7 and that are convex toward the inside and that satisfy the expression (1) in each of the sides 8 and 9 that make a pair In addition to improving the bending strength when an oblique load is input, this impact load causes plastic buckling deformation.

  For this reason, the crash box 3 can suppress the occurrence of bending deformation as a whole even with an impact load applied in an oblique direction with respect to the axial direction, and can be plastically buckled and deformed in a bellows shape. it can.

  4 (a) to 4 (d) show various types of crash boxes 3-1 to 3-4 having cross-sectional shapes obtained by modifying the basic cross-sectional shape of the crash box 3 according to the present invention shown in FIG. It is explanatory drawing which shows. Hereinafter, with respect to the crash boxes 3-1 to 3-4, portions that are different from the crash box 3 will be described, and common portions will be denoted by the same reference numerals, and redundant description will be omitted.

  The crash box 3-1 shown in FIG. 4A is the same as the crash box 3 shown in FIG. 3 except that the grooves 22 and 23 are provided not only on the paired sides 8 and 9 but also on the paired sides 10 and 11. Grooves 12, 13, 22, 23 are provided on all four sides 8-11.

  Compared with the crash box 3, the crash box 3-1 is more symmetrical with respect to the cross-sectional shape, so that the performance against oblique loads from various input directions is improved accordingly.

  The crash box 3-2 shown in FIG. 4B includes notches 24 and 25 formed in the crash box 3 by cutting the regions including the other corner portions 6 and 7 into a flat shape. Is. The widths W 'of the notches 24 and 25 are 5 times or more and less than 50 times, preferably less than 30 times the plate thickness t of the cylindrical body forming the crash box 3-2.

  When the notches 24 and 25 are provided, the side length W (mm) in the above formula (1) is the length of the side after being shortened by forming the notches 24 and 25. Means.

  A crash box 3-3 shown in FIG. 4C includes notches 26 and 27 formed by cutting a region including one corner portions 4 and 5 into a flat shape in the crash box 3-2. Is. The width W ′ of the notches 26 and 27 is not less than 5 times and less than 50 times, preferably less than 30 times the plate thickness t of the cylindrical body forming the crash box 3-3.

  Even when the notches 26 and 27 are provided, the side length W (mm) in the above formula (1) is the side after being shortened by forming the notches 26 and 27. Means the length of

The crash box 3-3 shown in FIG. 4D is formed by providing the notches 24 to 27 in the crash box 3-2 and is a new one that most governs the overall bending strength of the crash box 3-3. By making the curvature radii ρ _b of the vertices 28a to 28h larger than the curvature radii Rc of the corner portions 14 to 21 constituting the grooves 12 and 13, plastic buckling deformation is surely generated.

  If the ratio (W ′ / t) of the width (length) W ′ to the plate thickness t of these notches 24 to 27 is less than 5, plastic buckling in an accordion shape in the axial direction due to an applied impact load. When deforming, adjacent ridge lines are deformed synchronously, and plastic buckling deformation becomes unstable. On the other hand, if the ratio (W ′ / t) is more than 50, the buckling wavelength when continuous plastic buckling deformation occurs becomes long, and impact energy cannot be absorbed effectively.

In the crash boxes 3 to 3-4 described above, it is preferable that the corner boxes 4 and 5 are mounted on the vehicle body in the vertical direction.
In addition, in the crash boxes 3-2 to 3-4 shown in FIGS. 4B to 4D, the lengths W ′ of the notches 24 to 27 are 50 times or more the plate thickness t of the cylindrical body. Is provided at the positions excluding the corners at both ends of the notches 24 to 27, and provided with one or a plurality of grooves extending in the longitudinal direction and projecting toward the inside, and The plate thickness t (mm), length W ′ (mm), the number N of grooves, and the average value Wc (mm) of the opening widths of the N grooves are 5 <(W′−N × Wc). ) / (N + 1) / t <50, preferably 5 <(W′−N × Wc) / (N + 1) / t <30, when the impact load is applied and the material is crushed. This is desirable because the amount of out-of-plane deformation that occurs can be suppressed.

  Moreover, in the crash boxes 3-2 to 3-4 shown in FIG. 4C to FIG. 4D, the cylindrical body is joined by overlapping the edges of one constituent member, or in the axial direction. It is constituted by overlapping and joining the respective edges of a plurality of constituent members divided along, and a part of the above-mentioned notches 24 to 27, for example, the notches 24 and 25 or the notches 26, It is desirable that the reference numeral 27 denotes a superposed joint portion of one constituent member or a superposed joint portion of a plurality of constituent members.

  In particular, when the notches 24 and 25 are overlapped joints that are edges of one constituent member, or overlapped joints between a plurality of constituent members, an impact load due to a collision from an oblique direction is applied. As a result, the bending rigidity of the cylindrical body is improved, and it becomes possible to suppress the occurrence of a large bending deformation of the entire cylindrical body at the midpoint of the bellows-like plastic buckling deformation. Furthermore, when the joining of the overlap joint is continuous joining such as adhesion using a structural adhesive or continuous welding such as laser welding, for example, rather than intermittent joining such as spot welding, for example. This is desirable because the bending rigidity of the cylinder can be further increased.

  In these crash boxes 3 to 3-4, the direction in which the line passing through the pair of corner portions 4 and 5 is directed, or the direction in which the line passing through the other pair of corner portions 6 and 7 is directed is the vertical direction. Thus, by being attached to the vehicle body, it is possible to suppress the occurrence of bending deformation as a whole even with respect to an impact load that is input from an oblique direction with respect to the vehicle width or vehicle height direction. Since a stable bellows-like plastic buckling deformation can be generated, it is possible to ensure an excellent shock absorption characteristic, that is, a high shock absorption energy absorption amount even for an oblique collision.

Further, the present invention will be described more specifically with reference to examples.
About the plastic buckling behavior when a load from an oblique direction is input to the crash boxes 30 to 32 using the crash boxes 30 to 32 having the cross-sectional shapes shown in FIGS. investigated.

Note that the crash box 30 shown in FIG. 5 (a) and the crash box 31 shown in FIG. 5 (b) both have a pair of corner portions 33, 34 arranged opposite to each other, and the pair of corner portions 33. , 34 having a pair of other corner portions 35 and 36 arranged perpendicular to the line connecting the two, and having a quadrangular cross-sectional shape having no flange on the outside, and is divided along the axial direction. Each of the two component members 37a, 37b is a crush box composed of a metal cylinder configured by being partially overlapped and joined,
(A) In FIG. 5B, the angle formed by the pair of corner portions 33 and 34 and the angle formed by the other pair of corner portions 35 and 36 are both 90 °. The angle formed by the pair of corner portions 33 and 34 is 120 °, and the angle formed by the other pair of corner portions 35 and 36 is 60 °.
(B) the cross-sectional shape is symmetrical to both the line passing through the pair of corner portions 33 and 34 and the line passing through the other pair of corner portions 35 and 36;
(C) In all four sides constituting the quadrangular cross section, it extends in the longitudinal direction to a position excluding the pair of corner portions 33 and 34 and the other pair of corner portions 35 and 36 and is convex toward the inside. Having one groove 38;
(D) The thickness t (mm), the length W (mm) of the side, the number N of the grooves 38, and the average value Wc (mm) of the opening widths of the N grooves 38 are expressed by the formula (1): Satisfying the relationship of 5 <(W−N × Wc) / (N + 1) / t <50 (e) The region including the other pair of corner portions 35 and 36 is cut out in a planar shape. A notch 39 is formed, the notch 39 forms an overlapped joint between the plurality of constituent members 37a and 37b, and (f) the radius of curvature R of all the corners 33 to 36 is The curvature radius Rc is larger than any of the plurality of corners constituting the groove.

  Both Model A in FIG. 5A and Model B in FIG. 5B are examples of the present invention, and Model C in FIG. 5C is a comparative example. The thicknesses of Model A and Model B are 1.2 mm, the thickness of Model C is 1.4 mm, and the axial lengths of Models A to C are 200 mm. In the analysis, material characteristics assuming a 440 MPa class high-strength steel plate were used, and the strain rate dependency was further taken into consideration by the Cowper-Symmonds rule.

  As shown in FIG. 6, the analysis condition is that the rigid wall 41 is set to 10 degrees with respect to the module member 40 in which two crush boxes 30 to 32 having the cross-sectional shape shown in FIG. 5 are mounted on the bumper reinforcement 40 a. Collisions were performed at an angle of 16 km / h from an oblique direction, and the plastic buckling behavior of the crash boxes 30 to 32 was evaluated. The overlap rate of the rigid wall 41 with respect to the bumper reinforcement 40a is 40%.

  FIG. 7 is a graph showing comparison of load histories of the crash boxes 30 to 32. FIG. 8 is an explanatory diagram showing a deformation state of the crash boxes 30 to 32 at loading point displacements of 25 mm, 55 mm, and 90 mm.

  As shown in the graph of FIG. 7, Model A and Model B, which are examples of the present invention, show a high load and a small variation in load compared to Model C of the comparative example, despite being thin. Recognize.

  Further, as shown in FIG. 8, the model C of the comparative example generates a large buckling wrinkle on the side surface at the loading point displacement δ = 55 mm, and generates plastic buckling deformation at the anti-collision end at the loading point displacement δ = 90 mm. In contrast, Model A and Model B, which are examples of the present invention, show that fine buckling wrinkles are generated in order from the collision end. That is, it can be seen that, even when a bending moment is applied by inputting a load from an oblique direction, the present invention causes more stable plastic buckling deformation than the conventional example.

  FIG. 9 is a graph showing a comparison of the amount of out-of-plane deformation for the crash boxes 30 to 32. FIG. 9A shows the amount of out-of-plane deformation on the inner side surface in the vehicle width direction, and FIG. ) Indicates the amount of out-of-plane deformation on the outer side surface in the vehicle width direction.

  As shown in the graphs of FIGS. 9A and 9B, it can be seen that Model A and Model B, which are examples of the present invention, have a smaller amount of out-of-plane deformation than Model C, which is a comparative example. .

  In the present embodiment, the influence of the radius of curvature R of the corner portion and the radius of curvature Rc of a plurality of corner portions constituting the groove on the plastic buckling behavior when an impact load from an oblique direction is input to the crash box. In order to clarify the above, numerical analysis was conducted.

  FIG. 10 is an explanatory diagram showing the cross-sectional shape of the crash box 50 used for this analysis. In the analysis, for the member having an internal angle α = 90 degrees, the radii of curvature of the ridge lines constituting the groove 51 and the corner part 52 are respectively (a part: 2 mm, b part: 2 mm), (a part: 2 mm, The crush boxes 50a to 50c having a total of three types of cross-sectional shapes such as b part: 8 mm) and (a part: 2 mm, b part: 16 mm) were used. The a part means four ridge line parts constituting the groove 51, and the b part means a ridge line part constituting the corner part 52.

  The plate thickness of the crash boxes 50a to 50c is 1.2 mm, and the length in the axial direction is 200 mm. Moreover, the material characteristic which assumed the 440 MPa class high-tensile steel plate was used for the analysis, and also the strain rate dependence was considered in the Cowper-Symmonds rule.

  As shown in FIG. 11, the analysis condition is that the rigid wall 55 is 15 degrees with respect to the module member 54 in which the two crash boxes 50a to 50c having the cross-sectional shape shown in FIG. From the direction of 20 degrees, the plastic buckling behavior of the crash boxes 50a to 50c when colliding at a speed of 16 km / h was evaluated. The overlap rate of the rigid wall 55 with respect to the bumper reinforcement 53 is 40%.

FIG. 12 is an explanatory diagram showing a deformation state of the crash boxes 50a to 50c at the loading point displacement δ = 50 mm.
As shown in FIG. 12, when the collision angle is changed from 15 degrees to 20 degrees, an oblique load acting on the crash boxes 50a to 50c increases, and thus a large bending moment acts on the crash boxes 50a to 50c. . As a result, when the collision angle is 20 degrees, as compared with the case where the collision angle is 15 degrees, the amount of deviation from the broken line in the figure increases. It is getting bigger.

Furthermore, paying attention to the deformation diagram in the case of a collision angle of 20 degrees, and analyzing the influence of the curvature radius of the ridge line portion constituting the groove portion and the corner portion, the crash box 50a having a small curvature radius ρ _b of the corner portion, curvature radius [rho _b is greater crush box 50b, as compared to 50c, the ridge line of the inner axial center from the direction of the reaction collision end side member width direction (in the arrow), that a large bending deformation portion is generated Recognize. That is, the curvature radius [rho _b is small members, the rigidity of the corner portion is low, can not be suppressed by the bending deformation due to the bending moment generated on the crash box 50a by the inputted impact load in the width direction of the side surface A large out-of-plane displacement is caused, and as a result, continuous plastic buckling deformation in the axial direction necessary for obtaining a high amount of shock absorption energy cannot be generated.

  FIGS. 13 and 14 are graphs showing the results of comparing the out-of-plane displacements of the side surfaces on the inner side in the width direction of the halved product overlapping positions in the width direction of the crash boxes 50a to 50c. FIG. 13 shows a case where the collision angle is 15 degrees. FIG. 14 shows the result when the collision angle is 20 degrees.

In both results, on the collision end side (near x = 0), out-of-plane deformation occurred on the positive and negative side, and the peaks and valleys of the curve of the out-of-plane deformation overlapped, indicating that the buckling wrinkles overlapped. means.
13 and 14, when the collision angle is 15 degrees, the absolute value of the out-of-plane deformation is small and the surface in the anti-collision side direction is smaller than when the collision angle is 20 degrees. The external displacement is almost zero, and it can be seen that no bending deformation occurs as a whole.

On the other hand, when the collision angle is 20 degrees, out-of-plane deformation occurs from the center in the axial direction to the anti-collision end side, and it can be seen that the entire bending deformation occurs.
Next, comparing the amount of out-of-plane deformation between the crash boxes 50a to 50c, the crash box 50c with ρ _b = 16 mm has a crash box 50 a with ρ _b = 2 mm or a crash with ρ _b = 8 mm. It can be seen that the out-of-plane deformation is smaller than that of the box 50b, the out-of-plane deformation is most suppressed in the crash box 50c, and the degree of bending deformation is slight. That is, it can be seen that the larger the radius of curvature ρb, the smaller the degree of bending deformation when an oblique load is input.

Thus, by making the curvature radius ρ _b of all the corners larger than any of the curvature radii ρ _{a of} the plurality of corners constituting the groove, a load from an oblique direction is applied to the crash box. It is possible to suppress bending deformation as a whole, and thereby, plastic buckling deformation at a short buckling wavelength can be maintained, and a high impact energy absorption amount can be obtained .

It is explanatory drawing which shows typically the condition of what is called an offset collision. It is explanatory drawing which shows typically the input direction of the impact load to a crash box. It is explanatory drawing which shows the basic cross-sectional shape of the crash box which concerns on this invention. FIG. 4A to FIG. 4D are explanatory views showing various cross-sectional shape examples of the crash box according to the present invention. FIG. 5A to FIG. 5C are explanatory views showing the cross-sectional shape of the crush box analyzed in the first embodiment. It is explanatory drawing which shows analysis conditions. It is a graph which compares and shows the load history of a crash box. It is explanatory drawing which shows the deformation | transformation state in the loading point displacement 25mm, 55mm, 90mm of a crash box. FIG. 9A is a graph showing a comparison of the amount of out-of-plane deformation for a crash box, FIG. 9A shows the amount of out-of-plane deformation on the inner side surface in the vehicle width direction, and FIG. The amount of out-of-plane deformation on the side surface of It is explanatory drawing which shows the cross-sectional shape of the crush box used for the analysis of Example 2. FIG. It is explanatory drawing which shows analysis conditions. It is explanatory drawing which shows the deformation | transformation state in loading point displacement (delta) = 50mm about a crash box. It is a graph which shows the result of having compared the out-of-plane displacement of the side surface inside the width direction of the half product overlap position of the width direction of a crash box, and shows the case of a collision angle of 15 degrees. It is a graph which shows the result of having compared the out-of-plane displacement of the side surface inside the width direction of the half product overlap position of the width direction of a crash box, and shows the result in the case of a collision angle of 20 degrees.

Explanation of symbols

3,3-1 to 3-4 Crash box 4 according to the present invention, 5, a pair of corner portions 6, 7, and another pair of corner portions 8-11 side (plane portion)
12, 13, 22, 23 Groove 14-21 Corner 24-27 Notch 28a-28h Vertex 30-32 Crash box 33, 34 Pair of corners 35, 36 Other pair of corners 37a, 37b Constituent member 38 Groove 39 Notch 40a Bumper reinforcement 40 Module member 41 Rigid wall 50, 50a to 50c Crash box 51 Groove 52 Corner 53 Bumper reinforcement 54 Module member 55 Rigid wall

Claims (10)

A rectangular cross section having a pair of corner portions arranged opposite to each other and another pair of corner portions arranged perpendicular to a line connecting the pair of corner portions and having no flange on the outside A crash box composed of a metal cylinder having a shape,
The angle formed by the pair of corner portions is 90 ° or more and 150 ° or less, and the angle formed by the other pair of corner portions is 30 ° or more and 90 ° or less,
The cross-sectional shape is a shape symmetrical to a line passing through the pair of corner portions ,
The pair of corner portions provided on each of at least one pair of sides of the two pairs of sides arranged symmetrically with respect to a line passing through the pair of corner portions; It has one or a plurality of grooves that extend in the longitudinal direction and protrude toward the inside at positions excluding the corner portion, and has a plate thickness t (mm) and a side length W (mm) in each of all the sides. , The number N of grooves, and the average value Wc (mm) of the opening widths of the N grooves satisfy the relationship of the following formula (1) , and
The crash box according to claim 1, wherein the radius of curvature of all the corner portions is larger than the radius of curvature of any of the plurality of corner portions constituting the groove .
5 <(W−N × Wc) / (N + 1) / t <50 (1)   The crash box according to claim 1, wherein the groove is provided on all four sides. The crash according to claim 1, wherein the thickness t (mm) and the side length W (mm) of each pair of sides that are not provided with the groove satisfy the relationship of the following formula (2). box.
5 <(W / t) <50 (2)   The crash box according to any one of claims 1 to 3, wherein an angle formed by the pair of corner portions is larger than an angle formed by the other pair of corner portions. Furthermore, a region including at least one corner is provided with a notch formed by being cut out in a planar shape, and a thickness t (mm) and a length W ′ (mm) of the notch are expressed by the following formulas: The crash box according to any one of claims 1 to 4, wherein the relationship (3) is satisfied.
5 <(W ′ / t) <50 (3)
However, the length W (mm) of the side in the above formula (1) means the length of the side in a state where the notch is provided. Furthermore, a region including at least one corner portion of the pair of corner portions and the other pair of corner portions includes a notch portion formed by being cut out in a planar shape, and the length of the notch portion is And having one or a plurality of grooves that extend in the longitudinal direction at positions excluding the corners at both ends of the notch and are convex toward the inside, and are not less than 50 times the plate thickness of the cylindrical body, and The thickness t (mm), the length W ′ (mm), the number N of grooves, and the average value Wc (mm) of the opening widths of the N grooves are expressed by the following formula (4). The crash box according to any one of claims 1 to 4, wherein the crash box is satisfied.
5 <(W′−N × Wc) / (N + 1) / t <50 (4)
However, the length W (mm) of the side in the above formula (1) means the length of the side in a state where the notch is provided. The cylindrical body is configured by overlapping and joining the edges of one component member, or by overlapping and joining the edges of each of the plurality of component members divided along the axial direction, The crash box according to claim 5 or 6, wherein the notch is an overlapped joint portion of the one constituent member or an overlapped joint portion of a plurality of constituent members. The crash box according to any one of claims 1 to 7, wherein the crash box has a shape symmetrical to a line passing through another pair of corner portions. A rectangular cross section having a pair of corner portions arranged opposite to each other and another pair of corner portions arranged perpendicular to a line connecting the pair of corner portions and having no flange on the outside A crash box having a shape and a metal cylinder configured by overlapping and joining the respective edges of two component members divided along the axial direction. ,
The angle formed by the pair of corner portions and the angle formed by the other pair of corner portions are both 90 °,
The cross-sectional shape is symmetrical to both the line passing through the pair of corner portions and the line passing through the other pair of corner portions,
One or a plurality of grooves that extend in the longitudinal direction and protrude toward the inside at positions excluding the pair of corner portions and the other pair of corner portions on all four sides constituting the quadrangular cross section. Have
A region including the other pair of corner portions is provided with a notch portion formed by being cut out in a planar shape, and the notch portion constitutes an overlapping joint portion between the plurality of constituent members ,
The plate thickness t (mm), the length W (mm) of the side in the state where the notch portion is provided, the number N of grooves, and the average value Wc of the opening widths of the N grooves in each of all the sides. (Mm) satisfies the relationship of the following formula (1) ,
The thickness t (mm) and the length W ′ (mm) of the notch satisfy the relationship of the following formula (3) , and
The crush box characterized in that the curvature radius R of all the corner portions is larger than any curvature radius Rc of a plurality of corner portions constituting the groove .
5 <(W−N × Wc) / (N + 1) / t <50 (1)
5 <(W ′ / t) <50 (3) A direction in which a line passing through the pair of corner portions is directed, or a direction in which a line passing through the other pair of corner portions is directed to the crash box according to any one of claims 1 to 9. A structure for attaching a crash box to a vehicle body, which is characterized by being attached to the vehicle body in a vertical direction.

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