JP6488758B2 - Shock absorbing member - Google Patents

Description

  The present invention relates to an impact absorbing member that absorbs an impact load applied in an axial direction by periodic buckling.

  Shock absorbers are used in transport machines such as automobiles, railways, and ships. The impact absorbing member absorbs the energy of the collision by being deformed by receiving an impact load at the time of the collision, and as a result, it is possible to ensure the safety of the occupant and reduce the repair cost. Examples of such a shock absorbing member include an automobile skeleton member and a crash box.

  FIG. 1 is a perspective view schematically showing the arrangement of a skeleton member and a crash box in an automobile. As shown in the figure, a front side member 2, a rear side member 3, and a side sill 7 are disposed on the side of the automobile. All of these members are provided along the longitudinal direction of the automobile. The front side member 2 is arranged at the front part of the side part of the automobile, the rear side member 3 is arranged at the rear part of the side part of the automobile, and the side sill 7 is arranged at the middle part of the side part of the automobile.

  A floor (floor) is provided at an intermediate portion in the front-rear direction of the automobile. Floor cross members (4, 4 ') are arranged on the floor, and the floor cross members (4, 4') extend in the width direction of the automobile.

  The crash box (1a, 1b) is disposed at the tip of the frame formed of the above-described skeleton member. More specifically, the first crash box 1 a is provided at the front end of the front side member 2, and the second crash box 1 b is provided at the rear end of the rear side member 3.

  The frame members such as the front side member 2, the rear side member 3, the side sill 7 and the floor cross member (4, 4 '), and the crash box (1a, 1b) are loaded in the axial direction at the time of collision. There is a case. In this case, the impact load is absorbed by buckling and deforming such members so as to contract in a bellows shape in the axial direction.

  Such an impact-absorbing member can be produced by subjecting a metal plate as a material to bending or lap welding. The shock absorbing member produced from the metal plate has a cylindrical shape, that is, a shape in a cross section perpendicular to the axial direction is closed. For this reason, the inside of the shock absorbing member is hollow.

  Various proposals have hitherto been made regarding impact absorbing members that absorb impact loads by periodic buckling. Patent Document 1 describes a crash box. In addition to a member (main body) that forms a hollow cross section, the crush box includes an intermediate plate that extends horizontally so as to partition the hollow region up and down near the center in the vertical direction of the hollow cross section. By providing the intermediate plate, the crash box is prevented from buckling and collapsing at the time of collision, and is prevented from being bent. In the configuration example, the members (first member and second member) forming the hollow cross section and the third member forming the intermediate plate are both made of metal plates and have the same plate thickness.

Japanese Patent No. 4766422 Japanese Patent Application No. 2014-212231

Ayaki Gen and one other, “Energy Absorption Characteristics of Car Body”, Automobile Engineering Society Proceedings, No. 7, 1974, p. 60-66

  As described above, the impact absorbing member may be made of a metal plate. In this case, since the shape of the cross section perpendicular to the axial direction is closed, the inside of the shock absorbing member is hollow. Patent Document 1 describes that an intermediate plate is provided along the axial direction in a hollow portion of an impact absorbing member (main body).

  If the impact absorbing member is constituted by the main body and the middle plate in this way, the middle plate can surely assist the energy absorption by the main body. For this reason, the absorbed energy of the impact absorbing member can be increased, and it is effective, for example, in the impact absorbing member of a large vehicle.

  When the impact absorbing member is composed of a main body and an intermediate plate, conventionally, the main body is mainly responsible for energy absorption, and the intermediate plate is auxiliary. For this reason, the thickness of the intermediate plate was thinner than the thickness of the main body. Alternatively, as shown in the configuration example of Patent Document 1, the plate thickness of the middle plate is the same as the plate thickness of the main body.

  By the way, in the automobile, the weight reduction of components is requested | required from a viewpoint of a fuel consumption improvement. For this reason, the impact absorbing member is also required to be reduced in weight while ensuring the absorbed energy. Even in the impact absorbing member including the main body and the intermediate plate as described in Patent Document 1, it is required to reduce the weight while ensuring the absorbed energy.

  This invention is made | formed in view of such a problem, and it aims at providing the impact-absorbing member which can be reduced in weight, ensuring absorption energy.

  The shock absorbing member according to an embodiment of the present invention is a shock absorbing member including a main body and an intermediate plate formed from a metal plate, and the main body has a quadrangular shape in a cross section perpendicular to the axial direction. The intermediate plate is provided along the axial direction of the main body, and both ends in the width direction are overlapped and joined to the pair of long sides of the quadrangle, and further arranged in a predetermined region along the axial direction. A plurality of holes disposed in the center plate, and the predetermined region is located in the center in the width direction of the intermediate plate and is 39% wide (mm) with respect to the width (mm) of the intermediate plate. The thickness (mm) of the intermediate plate is 140 to 290% with respect to the thickness (mm) of the main body.

  The center interval (mm) of the plurality of holes is preferably 75 to 135% with respect to the buckling period (mm). The buckling period is calculated by calculating an average side length (mm) for each of the first and second quadrilaterals formed by dividing the quadrilateral with the intermediate plate, and calculating the average side length ( mm) is averaged.

  It is preferable that the length of the hole in the axial direction decreases as the hole approaches both ends in the width direction of the intermediate plate.

  The impact absorbing member of the present invention is located in the center in the width direction of the middle plate, and the holes are arranged in the axial direction of the main body in a region having a predetermined width. Further, the thickness of the middle plate is thicker than the thickness of the main body. As a result, the absorbed energy per unit mass can be improved, and the weight of the impact absorbing member can be reduced.

FIG. 1 is a perspective view schematically showing the arrangement of a skeleton member and a crash box in an automobile. FIG. 2A is a front view schematically showing a configuration example of the impact absorbing member of the present invention. FIG. 2B is a schematic diagram illustrating a configuration example of the shock absorbing member of the present invention, and is a cross-sectional view taken along line AA in FIG. 2A. FIG. 2C is a schematic diagram illustrating a configuration example of the shock absorbing member of the present invention, and is a cross-sectional view taken along line BB in FIG. 2A. FIG. 3A is a cross-sectional view illustrating the length of each side in the calculation of the average side length, and shows a case where the main body is made of one metal plate. FIG. 3B is a cross-sectional view illustrating the length of each side in the calculation of the average side length, and shows a case where the main body is made of two metal plates. FIG. 4A is a diagram illustrating a case where the hole is rectangular. FIG. 4B is a diagram illustrating a case where the hole has a diamond shape. FIG. 5 is a diagram showing the relationship between the width of the hole in the intermediate plate and the absorbed energy per unit mass. FIG. 6 is a diagram showing the relationship between the thickness of the intermediate plate and the absorbed energy ratio. FIG. 7 is a graph showing the relationship between the ratio of the center interval of the holes to the buckling period and the absorbed energy per unit mass. FIG. 8 is a diagram showing the relationship between the shape of the hole and the absorbed energy per unit mass.

1. Knowledge to Attain the Present Invention In the patent document 2, the present inventors have proposed that the thickness of the intermediate plate provided in the hollow portion is made thicker than the thickness of the main body having a closed cross section. By increasing the thickness of the middle plate, when the shock absorbing member periodically buckles and deforms, buckling deformation with different phases occurs on both sides of the middle plate, and the amplitude of the deformation (with buckling deformation) (The height of the peaks and the depth of the valleys) are reduced, and the wavelength (period) is shortened. Thereby, not only the absorbed energy of the impact absorbing member increases, but also the absorbed energy per unit mass can be increased. Therefore, even when the thickness of the main body is reduced, the absorbed energy can be secured and the weight can be reduced.

  On the other hand, in order to reduce the weight while securing the absorbed energy, the present inventors examined the removal of the meat by providing a hole in the intermediate plate. Here, the role of the intermediate plate is to suppress opening of the mouth when absorbing the shock. Mouth opening is a phenomenon in which, when the main body is periodically buckled and deformed, the long sides facing each other in the cross section of the main body are curved, and the distance between the long sides is widened at the center of the long side. In order to suppress such opening, both ends of the intermediate plate are joined to a pair of long sides in the cross section of the main body.

  Both end portions in the width direction of the intermediate plate are joined in a state of being folded and overlapped with a pair of long sides of the main body. At the time of impact absorption, a ridge line portion (bent R portion) formed along with bending of both ends also contributes to the impact absorption. This is because the ridge line portion of the intermediate plate is arranged along the axial direction of the main body.

  By the way, Non-Patent Document 1 discloses that the period of buckling deformation during shock absorption (hereinafter also referred to as “buckling period”) is the average side length (mm) of the closed cross section of the main body. Yes. If an intermediate plate is provided as in Patent Document 1, the closed cross section of the main body is partitioned by the intermediate plate and divided into two closed cross sections. In this case, the buckling period is an average of the average side lengths of the closed cross sections divided by the intermediate plate. For this reason, by providing the intermediate plate, the average side length of the shock absorbing member is reduced and the buckling period is also reduced, so that the shock absorbing ability is improved.

As a result of intensive studies in consideration of the role of the above-described intermediate plate and the buckling cycle in performing the lightening for providing a hole in the intermediate plate, the present inventors have found that the following (1) and (2) Obtained knowledge.
(1) When providing a hole in the intermediate plate, if a part of the hole is disposed in the ridge line portion, the shock absorbing ability is impaired. In other words, if the hole is arranged in the center region in the width direction of the intermediate plate, the shock absorbing ability can be secured.
(2) If the pitch (interval) of the holes is synchronized with the pitch (period) of buckling deformation, the periodic buckling deformation can be promoted, and the impact absorbing ability can be improved.

  Based on the findings of the above (1) and (2), the present inventors conducted the tests shown in the examples described later, and completed the above-described present invention. An embodiment of the present invention will be described below with reference to the drawings.

2. 2A to 2C are schematic views showing a configuration example of the shock absorbing member of the present invention, FIG. 2A is a front view, FIG. 2B is an AA cross-sectional view, and FIG. It is sectional drawing. The impact absorbing member 10 shown in the figure includes a main body 20 and an intermediate plate 30.

  As shown in FIG. B, the main body 20 has a quadrangular shape in a cross section (transverse cross section) perpendicular to the axial direction, and each side of the quadrangular shape is connected by a curve. The main body 20 shown in the figure has a rectangular shape in cross section, and each side of the rectangle is connected by an arc generated along with bending. The main body 20 is made of a single metal plate and has a closed cross section. Of the four sides of the quadrangle, one opposite side is a long side, and the other opposite side is a short side shorter than the long side.

  The middle plate 30 is made of a metal plate and is provided in the hollow portion of the main body 20 along the axial direction. The intermediate plate 30 has both ends joined to the main body 20, a linear portion provided between both ends, and a ridge line portion connecting the end and the linear portion. Further, both ends of the intermediate plate 30 are overlapped and joined to the pair of long sides 20 a among the four sides of the quadrangle of the main body 20. The intermediate plate 30 partitions the quadrangle of the main body 20, and the main body 20 and the intermediate plate 30 form two quadrangles.

  The intermediate plate 30 has a plurality of holes 30 a, and the holes 30 a are arranged side by side along the axial direction of the main body 20. In the middle plate 30 shown in FIG. 3C, elliptical holes are provided at equal intervals (pitch) in the center in the width direction of the middle plate 30. By providing the plurality of holes 30a in this manner, the lightening is achieved and the impact absorbing member can be reduced in weight.

  Further, the hole 30 a of the intermediate plate 30 is disposed in the predetermined region X. The region X is located at the center in the width direction of the intermediate plate 30 and extends along the axial direction of the main body 20. The width of the region X is 39% of the width W1 (mm) of the intermediate plate. However, the width W1 of the intermediate plate is the length of the linear portion of the intermediate plate 30.

  Here, as described above, the ridge line portion of the intermediate plate 30 contributes to shock absorption during shock absorption. On the other hand, the center of the middle plate 30 hardly contributes to shock absorption. If the hole 30a is disposed in the region X, since the hole does not enter the ridge line portion of the intermediate plate and the periphery thereof, the shock absorbing member can be reduced in weight while maintaining the shock absorbing action by the ridge line portion. Thereby, the absorbed energy per unit mass can be increased.

  When part or all of the hole 30a is located outside the region X, the absorbed energy per unit mass may be reduced. This is because the impact absorption effect by the ridge portion of the intermediate plate 30 is hindered, and the periodic buckling deformation becomes unstable at the time of impact absorption.

  The upper limit of the hole width Wh is naturally 100% of the width of the region X. The width Wh of the hole is preferably 50% or more with respect to the width of the region X from the viewpoint of promoting weight reduction.

  The plate thickness (mm) of the intermediate plate 30 is made thicker than the plate thickness (mm) of the main body 20 as in the above-described Patent Document 2. Specifically, the plate thickness (mm) of the intermediate plate 30 is set to 140 to 290% with respect to the plate thickness (mm) of the main body 20.

  If the plate thickness (mm) of the intermediate plate 30 is less than 140%, even if a hole is arranged in the region X, the absorbed energy per unit mass is reduced as shown in the examples described later. This is because the opening of the main body 20 cannot be suppressed, and the sides of the upper and lower spaces are too thin, and the balance during buckling is lost and stable buckling is inhibited.

  If the thickness (mm) of the intermediate plate 30 is 140 to 290%, by providing a hole in the region X, the absorbed energy can be improved while reducing the weight, and the absorbed energy per unit mass can also be improved. This is because, as will be clarified in Patent Document 2, periodic buckling deformation with different phases occurs on both sides of the intermediate plate 30, and the amplitude of the deformation becomes smaller and the wavelength becomes shorter. From the viewpoint of further improving the absorbed energy per unit mass, the thickness (mm) of the intermediate plate 30 is preferably 150% or more, and more preferably 220% or more. From the same viewpoint, the thickness (mm) of the intermediate plate 30 is preferably 285% or less, and more preferably 280% or less (see FIG. 6 described later).

  If the plate thickness (mm) of the intermediate plate 30 exceeds 290%, the absorbed energy per unit mass decreases even if holes are arranged in the region X, as shown in examples described later. This is due to the influence of the mass increase due to the thickening of the intermediate plate 30 and the fact that the sides of the upper and lower spaces become too thick, and the balance during buckling is lost and stable buckling is inhibited.

  The center interval (pitch) Ph of the holes 30a is not particularly limited, and may be appropriately set in consideration of workability when the intermediate plate 30 and the main body 20 are joined. Moreover, it is good also as an equal interval and good also as an unequal interval. The center interval Ph (mm) of the holes 30a is preferably 75 to 135% with respect to the buckling period (mm). The center interval Ph of the holes 30a is the interval in the axial direction of the main body.

Here, the buckling period is calculated by the following procedure.
(1) For the first and second quadrilaterals formed by partitioning the quadrilateral of the main body 20 with the intermediate plate 30, the average side length (mm) of the four sides is calculated.
(2) The average value of the average side length (mm) of the first quadrangle and the average side length (mm) of the second quadrangle is obtained and set as a buckling period.

  3A and 3B are cross-sectional views illustrating the length of each side in the calculation of the average side length. FIG. 3A shows a case where the main body is made of one metal plate, and FIG. The case of a plate is shown. In the calculation of the average side length (mm), the side length is the length of the linear portion excluding the ridge line portion. However, when the center of the ridge line portion is located outside the quadrangular shape, the portion existing outside the quadrangular shape is excluded. For example, in the lower quadrangular shape of the intermediate plate 30, the center of the ridge line portion that connects the side c and the side g is located outside the quadrangular shape. In this case, the side c extends linearly to the outside of the quadrangle, but the length of the side c is determined on the assumption that the side g extends to the side c. Similarly, the side e of FIG. 3A and the side d of FIG. 3B are excluded from the portion existing outside the quadrangular shape.

  If the center interval Ph (mm) of the holes 30a is 75 to 135% with respect to the buckling period (mm), the pitch of the holes 30a and the buckling pitch are synchronized. In this case, when the impact absorbing member is periodically buckled and deformed, the portion provided with the hole 30a is easily deformed into a mountain shape or a valley shape, so that the buckling pitch and the amplitude of the buckling deformation (the peak height) The depth of the valley is stable, and periodic buckling deformation is promoted. Thereby, the absorbed energy per unit mass can be further increased. For this reason, the impact absorbing member can be further reduced in weight.

  The shape of the hole 30a can be, for example, an ellipse, a rectangle, a rhombus, a square, a circle, or the like.

  4A and 4B are diagrams showing examples of hole shapes. FIG. 4A shows a case of a rectangle, and FIG. 4B shows a case of a diamond. In Examples described later, the shape of the hole 30a was an ellipse, a rectangle, or a rhombus, and the absorbed energy per unit mass was compared. As a result, it has been clarified that the absorption energy per unit mass is further increased when the ellipse and the rhombus are used. This is because, when the length Lh of the hole 30a (the length in the axial direction of the main body) is constant in the width direction of the intermediate plate like a rectangle, stress is concentrated at the corners, and the shock absorption by the ridge line portion of the intermediate plate This is because it adversely affects the action.

  In order to prevent this, it is preferable that the hole length Lh of the hole 30a becomes smaller as it approaches the both ends in the width direction of the intermediate plate. More specifically, the shape of the hole 30a is preferably an ellipse, a rhombus, or a circle.

  As described in Patent Document 2 described above, the thinner the main body, the greater the effect that the absorbed energy per unit mass is improved by increasing the thickness of the intermediate plate. For this reason, the plate thickness of the main body is preferably 2.3 mm or less, and more preferably 1.6 mm or less.

  Overlap joining of the main body and the intermediate plate can be performed by various methods as long as the main body and the intermediate plate can be integrally deformed without being separated at the time of collision. For example, overlap welding can be employed. In this case, for example, continuous welding or spot welding at a predetermined pitch can be employed.

  The main body can be made of, for example, a single metal plate. In this case, the metal plate may be bent so that the cross section has a polygonal shape, and as shown in FIG. As shown in FIG. 3B, the main body can also be manufactured by laminating and welding two metal plates, more specifically, a hat-shaped cross-sectional metal plate and a planar metal plate. In this case, the thickness of the two metal plates may be different. When the thicknesses of the two metal plates are different, in order to obtain the effect of the above-described embodiment, the thickness (mm) of the intermediate plate is the same as the thickness (mm) of any metal plate of the main body. The range.

  Both the main body and the intermediate plate are preferably made of a metal plate having a tensile strength of 270 to 1200 MPa. This is because the metal plate generally has a tensile strength of 270 MPa or more, and it is difficult to obtain a metal plate having a tensile strength of less than 270 MPa. Further, if the tensile strength exceeds 1200 MPa, cracks are likely to occur when the metal plate is processed, and the processing is difficult. The tensile strength of the metal plate is more preferably 440 to 980 MPa from the viewpoint of further increasing the absorbed energy and further suppressing the occurrence of cracks during processing.

  The impact absorbing member of this embodiment can be used as an impact absorbing member in a transport machine such as an automobile, a railway, or a ship. More specifically, if it is used as a shock absorbing member for an automobile, it can be used for a crash box or a skeleton member. In the case of a skeleton member, it can be used for a front side member, a rear side member, a side sill or a floor cross member.

  In order to confirm the effect of the impact absorbing member of this embodiment, an impact test was performed.

1. Confirmation test of hole arrangement region In this test, an analysis simulating a drop weight impact test was performed. Specifically, the impact absorbing member having the shape shown in FIG. 2 is dropped from a height of 16.1 m while a collision body having a mass of 700 kg is dropped in a state where the axial direction of the impact absorbing member is arranged along the vertical direction. It was made to collide with one end. At that time, the axial load and the axial displacement of the collision object were calculated, and the relationship between the load and the displacement was obtained.

  The impact absorbing member 10 has an axial length of 300 mm. The main body 20 had a rectangular cross section (quadrangle). In the main body 20, each of the pair of long sides (20a, 20b) has a straight portion length of 128 mm, and each of the pair of short sides has a straight portion length of 58 mm, and the ridge line portion is Was an arc having a radius of 6 mm.

  The middle plate 30 was arranged so that the linear portion of the middle plate 30 was located at the center of the pair of long sides of the main body 20. The length of the linear portion of the intermediate plate 30 (width W1 of the intermediate plate) was 55.2 mm, and the ridge line portion of the intermediate plate 30 was an arc having a radius of 6 mm. The middle plate 30 was provided with a plurality of elliptical or circular holes 30a arranged in the center in the width direction. The center interval Ph of the holes 30a of the intermediate plate 30 was set to an equal interval of 50 mm. The width Wh of the hole 30a is 10, 20, 22.5, 25, 30, 40, 50 or 60 mm, and the hole length Lh (maximum length in the axial direction of the main body) is 10, 20, 30 or 40 mm. It was.

  By dividing the quadrangle of the main body with an intermediate plate, first and second quadrangles were formed, and in FIG. 3A, the upper side was first and the lower side was second. In the upper first quadrangular shape, the length of side a was 58 mm, the length of side b was 58 mm, the length of side g was 55.2 mm, and the length of side f was 58 mm. Accordingly, the upper first quadrangular has an average side length of 57.3 mm.

  The lower second quadrangle had a side c length of 64 mm, a side d length of 58 mm, a side e length of 64 mm, and a side g length of 55.2 mm. Therefore, the lower second square had an average side length of 60.3 mm. From these average side lengths, the buckling cycle of the shock absorbing member was 58.8 mm.

  Both the main body 20 and the intermediate plate 30 were steel plates having a tensile strength of 980 MPa. The plate thickness of the main body 20 was 0.8 mm, and the plate thickness of the intermediate plate 30 was 2 mm. The joint between the main body 20 and the intermediate plate 30 sets boundary conditions that simulate spot welding, and more specifically, sets boundary conditions by simulating the case where spot welding with a diameter of 5 mm is performed at a pitch of 45 mm. .

  By calculating the absorbed energy (kJ) of the shock absorbing member from the relationship between the load and the displacement in the impact test and dividing the absorbed energy by the mass (kg) of the shock absorbing member, the absorbed energy per unit mass (kJ / kg) ) For comparison, an impact absorbing member in which the intermediate plate 30 does not have the hole 30a was subjected to a collision test under the same conditions, and the absorbed energy per unit mass (kJ / kg) was obtained.

  FIG. 5 is a diagram showing the relationship between the width (mm) of the hole in the intermediate plate and the absorbed energy per unit mass. The figure shows the relationship between the hole width of the intermediate plate and the absorbed energy per unit mass for each hole length. Moreover, the absorbed energy per unit mass is expressed as a relative value with an impact absorbing member having no hole in the middle plate as a reference (1).

  From the figure, there was a case where the absorbed energy per unit mass was reduced when the hole width exceeded 21.53 mm regardless of the length of the hole. That is, if a part of the hole is located outside the region that is located at the center in the width direction of the intermediate plate and 39% wide with respect to the width W1 (55.2 mm) of the intermediate plate, absorption per unit mass is achieved. There was a case where energy decreased.

  On the other hand, the absorbed energy per unit mass increased when the hole width was 21.53 mm or less regardless of the length of the hole. Therefore, if the hole is located in the center of the center plate in the width direction and 39% of the width of the center plate (55.2 mm), the absorbed energy per unit mass is increased. It became clear that we could do it.

2. Plate thickness confirmation test In this test, an impact test was performed using the impact absorbing member having the shape shown in Fig. 2 to obtain the absorbed energy per unit mass, as in the above-mentioned "Confirmation test of hole arrangement region". It was. In this test, the plate thickness of the main body was 0.8 mm, and the plate thickness of the intermediate plate was 0.8, 1.0, 1.2, 1.6, 2.0, 2.2, or 2.4 mm. Further, a case where the intermediate plate has a hole and a case where the intermediate plate does not have a hole were provided. In the case where the intermediate plate has holes, the shape of the holes was an ellipse having a width Wh of 20 mm and a length of Lh 40 mm, and the center interval Ph of the holes was an equal interval of 50 mm. The test conditions other than these were the same as those in the above-mentioned [Confirmation test of hole arrangement region].

  FIG. 6 is a diagram showing the relationship between the thickness (mm) of the intermediate plate and the absorbed energy ratio (no unit). The absorbed energy ratio in the figure shows the absorbed energy per unit mass of the case where the intermediate plate has holes (kJ / kg) for each thickness of the intermediate plate, and the unit energy of the case where the intermediate plate does not have holes. Divided by absorbed energy (kJ / kg).

  6 that the absorbed energy per unit mass increases when the thickness of the intermediate plate is 140 to 290% of the thickness of the main body.

3. Confirmation test of hole center interval In this test, an impact test was performed using the impact absorbing member having the shape shown in FIG. Asked. In this test, an intermediate plate having a hole was used, and the shape of the hole was an ellipse having a width Wh of 20 mm and a length of Lh 40 mm. The center interval Ph of the holes was set at an equal interval of 40, 45, 50, 60, 70 or 90 mm. The test conditions other than these were the same as those in the above-mentioned [Confirmation test of hole arrangement region].

  FIG. 7 is a graph showing the relationship between the ratio (%) of the hole center interval (mm) to the buckling period (mm) and the absorbed energy per unit mass. The absorbed energy per unit mass in the figure is expressed as a relative value with an impact absorbing member having no hole in the middle plate as a reference (1).

  From the figure, if the hole center interval (mm) is 75 to 135% with respect to the buckling period (58.8 mm), that is, 44.1 to 79.38 mm, absorption per unit mass. It became clear that energy increased.

4). Hole Shape Confirmation Test In this test, an impact test using the impact absorbing member having the shape shown in FIG. 2 is performed to obtain the absorbed energy per unit mass, as in the above-described [hole placement region confirmation test]. It was. The center interval Ph of the holes was an equal interval of 50 mm.

  The shape of the hole was an ellipse as shown in FIG. 2C, a rectangle as shown in FIG. 4A, or a rhombus as shown in FIG. 4B. In any hole shape, the hole width Wh was 20 mm and the hole length Lh was 40 mm. The test conditions other than these were the same as those in the above-mentioned [Confirmation test of hole arrangement region].

  FIG. 8 is a diagram showing the relationship between the shape of the hole and the absorbed energy per unit mass. The absorbed energy per unit mass in the figure is expressed as a relative value with an impact absorbing member having no hole in the middle plate as a reference (1).

  From the figure, when the ellipse and the rhombus were used, the absorbed energy per unit mass increased compared to the case where the hole was a rectangle. For this reason, it was confirmed that the absorbed energy per unit mass can be increased if the shape of the hole is an ellipse or a rhombus. In other words, it was confirmed that the absorbed energy per unit mass can be increased if the hole has a shape in which the length Lh in the axial direction decreases as it approaches both ends in the width direction of the intermediate plate.

  The impact absorbing member of the present invention can be reduced in weight while ensuring the absorbed energy. For this reason, if it applies to a crash box or a frame member of an automobile, it can greatly contribute to an improvement in fuel consumption.

10: Shock absorbing member, 20: Main body, 20a: Long side, 20b: Short side,
30: Middle plate, 30a: Hole, X: Area where holes are arranged in the present invention

Claims (3)

A shock absorbing member comprising a main body and an intermediate plate formed from a metal plate,
The main body has a quadrangular shape in a cross section perpendicular to the axial direction,
The intermediate plate is provided along the axial direction of the main body, and both ends in the width direction are overlapped and joined to the pair of long sides of the quadrangle, and further arranged in a predetermined region along the axial direction. Having a plurality of holes disposed within,
The predetermined region is located in the center in the width direction of the intermediate plate, and has a width (mm) of 39% with respect to the width (mm) of the intermediate plate,
The impact absorbing member, wherein a thickness (mm) of the intermediate plate is 140 to 290% with respect to a thickness (mm) of the main body. The shock absorbing member according to claim 1,
The center interval (mm) of the plurality of holes is 75 to 135% with respect to the buckling period (mm),
The buckling period is calculated by calculating an average side length (mm) for each of the first and second quadrilaterals formed by dividing the quadrilateral with the intermediate plate, and calculating the average side length ( mm), which is an average of (mm). The impact absorbing member according to claim 1 or 2,
The impact absorbing member, wherein the hole has a length in the axial direction that decreases as the hole approaches both ends in the width direction of the intermediate plate.