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CN-122029096-A - Impact absorbing member and vehicle body

CN122029096ACN 122029096 ACN122029096 ACN 122029096ACN-122029096-A

Abstract

The impact absorbing member is provided on the vehicle body and is formed along a predetermined longitudinal direction, and the impact absorbing member includes a closed cross-sectional portion having a closed cross-sectional shape in a cross-section orthogonal to the longitudinal direction. The impact absorbing member includes a low-strength portion, a high-strength portion which is arranged with the low-strength portion and has a plate-thickness-direction center portion having a higher Vickers hardness than the plate-thickness-direction center portion of the low-strength portion, and a joining portion which joins the low-strength portion and the high-strength portion. The maximum bending angle of the high-strength portion is set according to the maximum bending angle of the low-strength portion.

Inventors

  • ONO ATSUSHI

Assignees

  • 日本制铁株式会社

Dates

Publication Date
20260512
Application Date
20241016
Priority Date
20231018

Claims (16)

  1. 1. An impact absorbing member provided in a vehicle body and formed along a predetermined longitudinal direction, the impact absorbing member including a portion having a closed cross-sectional shape in a cross section orthogonal to the longitudinal direction, The impact absorbing member is provided with: A low-strength portion; A high-strength portion arranged in the longitudinal direction with the low-strength portion and having a plate-thickness-direction central portion having a higher Vickers hardness than the plate-thickness-direction central portion of the low-strength portion, and A joining portion joining the low-strength portion and the high-strength portion, The maximum bending angle of the high-strength portion is set according to the maximum bending angle of the low-strength portion.
  2. 2. The impact-absorbing member according to claim 1, wherein, The difference between the maximum bending angle of the high-strength portion and the maximum bending angle of the low-strength portion is 100 degrees or less.
  3. 3. The impact-absorbing member according to claim 1, wherein, The Vickers hardness of the high-strength portion at the center in the plate thickness direction is 500HV or more.
  4. 4. The impact-absorbing member according to claim 3, wherein, The Vickers hardness of the plate thickness direction central part of the low-strength part is more than 150 HV.
  5. 5. The impact-absorbing member according to claim 3, wherein, The ratio HV 1 /HV 2 of the Vickers hardness HV 1 of the high-strength portion and the Vickers hardness HV 2 of the low-strength portion is 1.3 or more.
  6. 6. The impact-absorbing member according to claim 1, wherein, The difference between the maximum bending angle of the low-strength portion and the maximum bending angle of the high-strength portion is 30 degrees or less.
  7. 7. The impact absorbing member according to any one of claims 1 to 6, wherein, The impact absorbing member is a center pillar provided with an inner pillar member and an outer pillar member and arranged along the up-down direction of the vehicle body, The column outer member includes the low-strength portion, the joint portion, and the high-strength portion, The high-strength portion is disposed above the low-strength portion.
  8. 8. The impact-absorbing member of claim 7, wherein, The center pillar is provided with an upper and a lower pair of brackets for supporting a door provided at the rear of the center pillar, The joint is disposed at a position lower than a height position of a lower end of the bracket on an upper side.
  9. 9. The impact-absorbing member of claim 8, wherein, The joint is disposed at a position higher than the height position of the upper end of the bracket on the lower side.
  10. 10. The impact-absorbing member of claim 8, wherein, The joint is disposed at a position lower than a height position of a lower end of the bracket at a lower side.
  11. 11. The impact-absorbing member of claim 7, wherein, The vehicle body further includes a rocker joined to a lower portion of the center pillar and disposed along a front-rear direction of the vehicle body, the rocker having a closed cross-sectional shape in a cross section orthogonal to the front-rear direction, The rocker includes an outer side wall disposed on an outer side in the width direction of the vehicle body in the rocker, The lower part of the center pillar is provided with an overlapping part which is configured to cover the lower side beam at a connecting part connected with the lower side beam, The overlapping portion extends to a position below a height position of half of the outer side wall in the up-down direction of the rocker.
  12. 12. The impact-absorbing member according to claim 1, wherein, The surface of the high-strength portion in the plate thickness direction has a Vickers hardness at least 100HV lower than that of the central portion in the plate thickness direction.
  13. 13. The impact-absorbing member of claim 12, wherein, The high-strength portion is provided with a high-strength portion softening layer in the plate thickness direction from the surface, In the high-strength portion, the Vickers hardness of the central portion in the plate thickness direction at the portion where the high-strength portion softening layer is provided is 500HV or more, The thickness of the high-strength portion softening layer is 80 μm or more and is 5% to 20% of the plate thickness at the portion where the high-strength portion softening layer is provided, The Vickers hardness of the high-strength portion softening layer at the surface is 0.5 times or more and less than 0.9 times the Vickers hardness of the plate thickness direction central portion at a portion where the high-strength portion softening layer is provided, The high-strength portion softening layer has a first hardness change region which is a region from the surface to 40% of the thickness of the high-strength portion softening layer in the plate thickness direction, and a second hardness change region which is a region of the high-strength portion softening layer other than the first hardness change region, An absolute value Δhv1 of the hardness change in the plate thickness direction in the first hardness change region is larger than an absolute value Δhv2 of the hardness change in the plate thickness direction in the second hardness change region.
  14. 14. The impact-absorbing member according to claim 1, wherein, The surface of the low-strength portion in the plate thickness direction has a Vickers hardness at least 100HV lower than the Vickers hardness of the central portion in the plate thickness direction of the low-strength portion.
  15. 15. The impact-absorbing member of claim 14, wherein, The low-strength portion is provided with a low-strength portion softening layer from the surface in the plate thickness direction, In the low-strength portion, the Vickers hardness of the plate thickness direction central portion at the portion where the low-strength portion softening layer is provided is 150HV or more, The low-strength portion softening layer has a thickness of 80 μm or more and a thickness of 5% or more and 20% or less of a plate thickness at a portion where the low-strength portion softening layer is provided, The Vickers hardness of the low-strength portion softening layer at the surface is 0.5 times or more and less than 0.9 times the Vickers hardness of the plate thickness direction central portion at a portion where the low-strength portion softening layer is provided, The low-strength portion softening layer has a first hardness change region which is a region from the surface to 40% of the thickness of the low-strength portion softening layer in the plate thickness direction, and a second hardness change region which is a region of the low-strength portion softening layer other than the first hardness change region, An absolute value Δhv1 'of the hardness change in the plate thickness direction in the first hardness change region is larger than an absolute value Δhv2' of the hardness change in the plate thickness direction in the second hardness change region.
  16. 16. A vehicle body, wherein, The vehicle body is provided with a center pillar and a rocker joined to a lower portion of the center pillar, At least one of the center pillar and the rocker is the impact absorbing member of claim 1.

Description

Impact absorbing member and vehicle body Technical Field The present invention relates to an impact absorbing member and a vehicle body. Background The automobile is required to reduce the CO 2 emission, and on the other hand, the standard value of collision safety is becoming strict. Therefore, for automobile members such as impact absorbing members, weight saving and improved collision safety are demanded, and material selection and structural design of the impact absorbing members are important. Particularly, for a center pillar, which is an important member for protecting an occupant in a side collision of an automobile, a higher level of knowledge is required in terms of material selection and structural design. The upper portion of the center pillar requires a high load-bearing capacity to prevent deformation from the viewpoint of protecting the occupant, and therefore the application of a high-strength material is effective. On the other hand, the lower portion of the center pillar is required to absorb energy, and therefore, a material having a good balance between strength and fracture resistance is required. Therefore, a Tailor Welded Blank (TWB) in which two different materials can be arranged in 1 blank is useful as a material for a center pillar from the viewpoint of weight reduction. As the TWB material, the TWB material described in patent document 1 can be exemplified. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2023-55526 Disclosure of Invention Problems to be solved by the invention From the standpoint of reducing the amount of CO 2 emissions, each automobile manufacturer is accelerating the development of a push electric vehicle. In an automobile such as a gasoline engine vehicle or a diesel engine vehicle that transmits an output rotation of an internal combustion engine to wheels, a rocker is largely deformed in a rotating manner at the time of a side collision of the automobile, and a center pillar tends to be deformed at the same time. Thus, the deformation of the center pillar is localized. On the other hand, in the electric vehicle, a battery is disposed on a side of the rocker. In order to protect the battery, a shock absorbing member or the like for protecting the battery is provided in the rocker to reinforce the rocker, and the rocker is not easily deformed. In this way, in an electric vehicle in which the rocker is less likely to deform in terms of the structure of the protection battery, the deformation amount of the rocker is relatively small at the time of a side collision, and accordingly, the deformation amount of the center pillar tends to increase by absorbing an impact. In particular, in the center pillar outer member formed of TWB and having an upper portion having a higher tensile strength than a lower portion, the lower end portion of the upper portion (portion near the weld line with the lower portion) having a high strength is also greatly deformed by being dragged by the deformation of the lower portion having a low strength, and there is a possibility that the base material is broken. From the viewpoint of securing impact absorption performance, it is preferable that the possibility of fracture of the base material does not occur, and therefore it is preferable to suppress such possibility of fracture of the base material. In order to suppress the possibility of fracture of the base material, it is considered to increase the plate thickness of the center pillar outer member, but increasing the plate thickness of the center pillar outer member causes an increase in the weight of the center pillar outer member, which is not preferable. In order to reduce the weight of the center pillar outer member and improve the impact absorption performance at the time of a side collision, it is preferable to make the steel sheet constituting the center pillar outer member thin and high-strength, and further to suppress the possibility of breakage of the member at the time of a side collision. An object of the present invention is to provide an impact absorbing member that is lighter and can achieve high collision resistance, and a vehicle body provided with the impact absorbing member. Solution for solving the problem The gist of the present invention is the following impact absorbing member and vehicle body. (1) An impact absorbing member provided in a vehicle body and formed along a predetermined longitudinal direction, the impact absorbing member including a portion having a closed cross-sectional shape in a cross section orthogonal to the longitudinal direction, The impact absorbing member is provided with: A low-strength portion; A high-strength portion arranged in the longitudinal direction with the low-strength portion and having a plate-thickness-direction central portion having a higher Vickers hardness than the plate-thickness-direction central portion of the low-strength portion, and A joining portion joining the