Door impact beam, side door of automobile, and automobile

Abstract

This door impact beam (10) is used for a side door of an automobile. The door impact beam (10) comprises a first plate portion (21), a second plate portion (22), a first end flange portion (31), and a second end flange portion (32). The first plate portion (21) extends in the longitudinal direction of the door impact beam (10). The second plate portion (22) extends in the longitudinal direction and is connected to one side portion (21a) of the first plate portion (21) with a ridge portion (221) therebetween. The first end flange portion (31) is connected to an end portion (21c) in the longitudinal direction of the first plate portion (21). The second end flange portion (32) is connected to an end portion (22c) in the longitudinal direction of the second plate portion (22). The second end flange portion (32) is inclined with respect to the longitudinal direction and is continuous with the first end flange portion (31).

Description

Door impact beam, automobile side door, and automobile

[0001] The present disclosure relates to a door impact beam for use in a side door of a motor vehicle. The present disclosure also relates to a side door of a motor vehicle and a motor vehicle each using a door impact beam.

[0002] Automobiles are required to have a high level of crashworthiness, and are required to have a structure that can ensure interior space to protect occupants in the event of a collision. Possible collision types for automobiles include side collisions, full-overlap frontal collisions, and small-overlap frontal collisions. To ensure crashworthiness, the side doors of automobiles are required to absorb the impact of a collision and prevent excessive deformation toward the interior of the vehicle. Furthermore, automobiles are also required to have lightweight bodies in order to improve fuel efficiency. Therefore, side doors are required to achieve both crashworthiness and lightweight design.

[0003] In recent years, electric vehicles (EVs) have become increasingly popular. EVs have large batteries mounted under the vehicle body. This increases the vehicle body weight, which can lead to excessive deformation of the side door toward the interior of the vehicle during a collision, potentially damaging the battery. If the battery is damaged during a collision, secondary damage such as a fire can occur. To avoid such secondary damage, it is also necessary to protect the battery during a collision. Furthermore, vehicle weight reduction is also required to improve fuel economy. Therefore, among all automobiles, the side doors of EVs are particularly required to combine crashworthiness with lightweight design.

[0004] In order to improve the crashworthiness of a side door, a door impact beam is sometimes provided inside the side door (for example, see Patent Documents 1 and 2). The door impact beam is typically joined to the door body that constitutes the side door.

[0005] Patent Documents 1 and 2 describe door structures including a door impact beam. In the door structure described in Patent Document 1, the end of the door impact beam (door member) is divided into three parts in the vertical direction. Specifically, the end of the door impact beam is divided into two bent parts located on the upper and lower sides, and a flat part located between these bent parts. The door impact beam is joined to an inner panel that constitutes a door body at the flat part and the two bent parts.

[0006] In the door structure described in Patent Document 2, a door hinge is attached to a front wall of an inner panel that constitutes a door body. A door impact beam (impact bar) is joined to the door hinge with bolts and nuts.

[0007] JP 2-241821 A JP 2009-18768 A

[0008] In the door structure of Patent Document 1, there is a risk that damage will progress from the roots of the three divided ends of the door impact beam during a collision. In addition, in the door structure of Patent Document 2, the collision load will be concentrated on the joint (bolt and nut) between the door impact beam and the door hinge, which may cause damage to the joint.

[0009] An object of the present disclosure is to provide a door impact beam that can achieve both crashworthiness in a frontal collision and lightweight construction. Another object of the present disclosure is to provide a side door of an automobile and an automobile that each use such a door impact beam.

[0010] The door impact beam according to the present disclosure is used in a side door of an automobile. The door impact beam comprises a first plate portion, a second plate portion, a first end flange portion, and a second end flange portion. The first plate portion extends in the longitudinal direction of the door impact beam. The second plate portion extends in the longitudinal direction and is connected to one side portion of the first plate portion via a ridge portion. The first end flange portion is connected to an end portion of the first plate portion in the longitudinal direction. The second end flange portion is inclined with respect to the longitudinal direction and is continuous with the first end flange portion.

[0011] The automobile side door according to the present disclosure includes a door body and the door impact beam joined to the door body.

[0012] The automobile according to the present disclosure includes a side door including a door body and the door impact beam joined to the door body.

[0013] The door impact beam, automobile side door, and automobile according to the present disclosure can achieve both crash resistance performance in frontal collisions and lightweight design.

[0014] FIG. 1 is a schematic diagram showing the overall configuration of an automobile. FIG. 2 is a schematic diagram of a front door. FIG. 3 is a perspective view of a door impact beam according to the first embodiment. FIG. 4 is a perspective view of a door impact beam according to the first embodiment. FIG. 5 is a cross-sectional view of a beam body. FIG. 6 is a cross-sectional view of a beam body of a door impact beam according to a second embodiment. FIG. 7 is a partially enlarged view of FIG. 6. FIG. 8 is a cross-sectional view of a modified beam body. FIG. 9 is a cross-sectional view of a modified beam body. FIG. 10 is a perspective view of a modified door impact beam. FIG. 11 is a perspective view of a modified door impact beam. FIG. 12 is a diagram summarizing the results of the examples. FIG. 13 is a diagram summarizing the results of the examples.

[0015] The door impact beam according to the embodiment is used in a side door of an automobile. The door impact beam comprises a first plate portion, a second plate portion, a first end flange portion, and a second end flange portion. The first plate portion extends in the longitudinal direction of the door impact beam. The second plate portion extends in the longitudinal direction and is connected to one side of the first plate portion via a ridge portion. The first end flange portion is connected to an end of the first plate portion in the longitudinal direction. The second end flange portion is connected to an end of the second plate portion in the longitudinal direction. The second end flange portion is inclined with respect to the longitudinal direction and is continuous with the first end flange portion (first configuration).

[0016] In the first configuration, the end of the door impact beam includes a first end flange portion of the first plate portion and a second end flange portion of the second plate portion. The first end flange portion and the second end flange portion form a continuous flange portion. At least a portion of the continuous flange portion, i.e., the second end flange portion, is inclined relative to the longitudinal direction. By joining this continuous flange portion to the door body constituting the side door, the continuous flange portion, which serves as the joint surface with the door body, becomes continuous, thereby increasing the area of ​​the joint surface. This allows for the load caused by a frontal collision to be distributed. Therefore, the door impact beam of the first configuration can ensure high crash resistance against a frontal collision. The improved crash resistance allows for a thinner plate, thereby reducing the weight of the door impact beam. As a result, both crash resistance and weight reduction can be achieved.

[0017] In the door impact beam, the first plate portion and the second plate portion may each be flat (second configuration).

[0018] In the door impact beam, the second end flange portion may be flush with the first end flange portion (third configuration).

[0019] In the door impact beam, the second end flange portion may be on a different plane from the first end flange portion (fourth configuration).

[0020] The door impact beam may further include a first side flange portion. The first side flange portion extends in the longitudinal direction and is connected to a side portion of the second plate portion opposite the first plate portion via a ridge portion. The first side flange portion is continuous with the second end flange portion. A ridge portion is formed between the second end flange portion and the first side flange portion (fifth configuration). The door impact beam of the fifth configuration includes a first side flange portion. A ridge portion is formed between the second plate portion and the first side flange portion. In this case, the second plate portion is connected to the first plate portion via a ridge portion and is further connected to the first side flange portion via a ridge portion. As a result, the door impact beam of the fifth configuration has an increased number of ridge portions extending in the longitudinal direction, thereby further improving crash resistance.

[0021] The door impact beam may further include a third plate portion and a third end flange portion. The third plate portion extends in the longitudinal direction and is connected to the other side of the first plate portion via a ridge portion. The third end flange portion is connected to an end of the third plate portion. The third end flange portion is inclined with respect to the longitudinal direction and is continuous with the first end flange portion (sixth configuration). In the door impact beam of the sixth configuration, in addition to a ridge portion being provided between the first plate portion and the second plate portion, a ridge portion is also provided between the first plate portion and the third plate portion. Therefore, the door impact beam of the sixth configuration can ensure higher crash resistance.

[0022] The door impact beam of the sixth configuration may further include a second side flange portion. The second side flange portion extends in the longitudinal direction and is connected to a side portion of the third plate portion opposite the first plate portion via a ridge portion. The second side flange portion is continuous with the third end flange portion. A ridge portion is formed between the third end flange portion and the second side flange portion (seventh configuration). The door impact beam of the seventh configuration includes a second side flange portion. A ridge portion is formed between the third plate portion and the second side flange portion. In this case, the third plate portion is connected to the first plate portion via a ridge portion and is further connected to the second side flange portion via a ridge portion. As a result, the door impact beam of the seventh configuration has an increased number of ridge portions extending in the longitudinal direction, thereby further improving crash resistance.

[0023] In the door impact beam, the first end flange portion and the second end flange portion may be provided at both ends of the door impact beam, respectively (eighth configuration).

[0024] In the door impact beam, the first end flange portion and the second end flange portion may each be provided only at one end of the door impact beam (ninth configuration).

[0025] At least a portion of the door impact beam may be formed of a plate-shaped surface-softened portion, the Vickers hardness of the surface of the surface-softened portion being lower than the Vickers hardness of the surface of the surface-softened portion at the center in the plate thickness direction (tenth configuration). In the tenth configuration, the Vickers hardness of the surface of the surface-softened portion is lower than the Vickers hardness of the surface of the surface-softened portion at the center in the plate thickness direction, thereby improving the bending deformability of the surface-softened portion and making it easier for the surface-softened portion to absorb impact.

[0026] The door impact beam of the tenth configuration preferably has the following configuration: The surface-softened portion is formed of a hardened portion and a softened portion. The softened portion is laminated on the hardened portion. The Vickers hardness of the surface-softened portion at the center in the plate thickness direction is 400 HV or more. The thickness of the softened portion is 80 μm or more and 5% to 20% of the plate thickness of the surface-softened portion. The Vickers hardness of the surface of the surface-softened portion is 0.5 to less than 0.9 times the Vickers hardness of the surface of the surface-softened portion at the center in the plate thickness direction. The softened portion includes a first region and a second region. The first region is a region from the surface of the surface-softened portion to 40% of the thickness of the softened portion. The second region is a region of the softened portion excluding the first region. The absolute value ΔHV1 of the change in Vickers hardness in the thickness direction in the first region is greater than the absolute value ΔHV2 of the change in Vickers hardness in the thickness direction in the second region (eleventh configuration).

[0027] In the eleventh configuration, the Vickers hardness of the surface-softened portion at the center in the plate thickness direction is 400 HV or more, so the deformability of the surface-softened portion is likely to be significantly improved. Furthermore, the thickness of the softened portion is 20% or less of the plate thickness of the surface-softened portion, so the ratio of the volume of the softened portion to the total volume of the surface-softened portion is small, and the load-bearing capacity of the surface-softened portion can be ensured. Furthermore, the thickness of the softened portion is 80 μm or more and 5% or more of the plate thickness of the surface-softened portion, so the deformability of the softened portion can be fully exhibited.

[0028] In the eleventh configuration, the Vickers hardness of the surface of the softened surface portion is 0.5 times or more the Vickers hardness of the center of the softened surface portion in the thickness direction, thereby improving the load-bearing capacity during a collision, particularly in the later stage of the stroke during a collision. Furthermore, the Vickers hardness of the surface of the softened surface portion is less than 0.9 times the Vickers hardness of the center of the softened surface portion in the thickness direction, thereby sufficiently improving the deformability of the softened surface portion. Furthermore, in the eleventh configuration, ΔHV1 is greater than ΔHV2, thereby improving the crashworthiness of the softened surface portion.

[0029] A side door of an automobile according to an embodiment includes a door body and the door impact beam joined to the door body (twelfth configuration).

[0030] The side door preferably has the following configuration: the door main body includes a door hinge portion, and the first end flange portion and the second end flange portion are each joined to the door hinge portion (thirteenth configuration).

[0031] In the above-mentioned side door, the first end flange portion and the second end flange portion may each be joined to a front edge portion of the door body (fourteenth configuration). In the side door of the fourteenth configuration, a continuous flange portion of the door impact beam formed by the first end flange portion and the second end flange portion is joined to the front edge portion of the door body. This effectively improves crash resistance in a frontal collision.

[0032] The side door may be a front door of a vehicle (fifteenth configuration).

[0033] An automobile according to an embodiment includes a side door including a door body and the door impact beam joined to the door body (sixteenth configuration).

[0034] The automobile preferably has the following configuration: the door body includes a door hinge portion, and the first end flange portion and the second end flange portion are each joined to the door hinge portion (seventeenth configuration).

[0035] In the above-described vehicle, the first end flange portion and the second end flange portion may each be joined to a front edge portion of the door body (18th configuration).

[0036] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0037] [First embodiment] [Overall configuration of automobile] Fig. 1 is a schematic diagram showing the overall configuration of an automobile 1. Referring to Fig. 1, the automobile 1 has side doors, that is, a front door 2 and a rear door 3. Only the configuration of the front door 2 will be described in detail below, but the rear door 3 has substantially the same configuration as the front door 2.

[0038] Fig. 2 is a schematic diagram of the front door 2. Fig. 2 shows the front door 2 as viewed from the inside of the vehicle. Referring to Fig. 2, the front door 2 includes a door body 4 and a window frame 5 joined to the door body 4. The door body 4 includes an inner panel 6 and an outer panel (not shown). The outer panel is joined to the outside of the inner panel 6.

[0039] The door body 4 includes a belt line portion 4a extending in the vehicle length direction of the automobile 1. The belt line portion 4a corresponds to the lower edge of the window frame 5. The front door 2 includes two door impact beams, i.e., a first door impact beam 10a and a second door impact beam 10b, as reinforcing members for enhancing collision resistance.

[0040] The first door impact beam 10a is disposed along the vehicle length direction. The position where the first door impact beam 10a is disposed is not particularly limited. In the example shown in FIG. 2, the first door impact beam 10a is disposed below the belt line portion 4a. However, the first door impact beam 10a may be disposed at the position of the belt line portion 4a in the vehicle height direction. The first door impact beam 10a disposed at the position of the belt line portion 4a is sometimes called a belt line reinforcement.

[0041] The second door impact beam 10b is positioned lower than the first door impact beam 10a in the vehicle height direction of the automobile 1. The second door impact beam 10b is positioned at an angle relative to the vehicle length direction. Hereinafter, when there is no need to distinguish between the first door impact beam 10a and the second door impact beam 10b, they may be simply referred to as the "door impact beam 10."

[0042] The door main body 4 includes a door hinge portion 4b. The door hinge portion 4b serves as a fulcrum when the front door 2 is opened or closed. The front door 2 is attached to the body of the automobile 1 via the door hinge portion 4b. The door hinge portion 4b is fixed to the door main body 4 while passing through a front edge portion 4c of the door main body 4 in the vehicle length direction. In the example shown in FIG. 2 , two door hinge portions 4b are arranged spaced apart in the vehicle height direction.

[0043] The first door impact beam 10a and the second door impact beam 10b are each joined to the door body 4. Specifically, the front end of the first door impact beam 10a is joined to the door hinge portion 4b, and the rear end is joined to the rear edge 4d of the door body 4 (inner panel 6). The front end of the second door impact beam 10b is joined to the front edge 4c of the door body 4 (inner panel 6), and the rear end is joined to the rear edge 4d of the door body 4 (inner panel 6).

[0044] Because the front end of the first door impact beam 10a is joined to the door hinge portion 4b, the first door impact beam 10a is not directly joined to the inner panel 6. In this case, the transmission of the load from the first door impact beam 10a to the inner panel 6 is suppressed, and the load burden on the inner panel 6 can be reduced.

[0045] [Door Impact Beam] Next, the door impact beam 10 according to the first embodiment will be described with reference to Figures 3 to 5. As described above, the door impact beam 10 is used in the side door of the automobile 1. Figures 3 and 4 are perspective views of the door impact beam 10. Figure 3 shows the front end of the door impact beam 10, and Figure 4 shows the rear end of the door impact beam 10.

[0046] 3 and 4, the door impact beam 10 includes a beam body 20 and continuous flange portions 30, 40. The beam body 20 extends in the longitudinal direction of the door impact beam 10. The continuous flange portions 30, 40 form the front and rear ends of the beam body 20 in the longitudinal direction.

[0047] FIG. 5 is a cross-sectional view of the beam body 20. The cross-section refers to a cross-section taken perpendicular to the longitudinal direction of the door impact beam 10. Referring to FIGS. 3 to 5, in this embodiment, the beam body 20 has a hat-shaped cross-section. The beam body 20 includes a first plate portion 21, a second plate portion 22, a third plate portion 23, a first side flange portion 24, and a second side flange portion 25. The first plate portion 21, the second plate portion 22, the third plate portion 23, the first side flange portion 24, and the second side flange portion 25 each extend in the longitudinal direction of the door impact beam 10.

[0048] In this embodiment, the first plate portion 21 corresponds to the top plate of the hat-shaped beam body 20, and the second plate portion 22 and the third plate portion 23 correspond to the vertical walls of the beam body 20. Hereinafter, the width direction of the first plate portion 21 may be referred to as the width direction of the door impact beam 10, and the direction perpendicular to the first plate portion 21 may be referred to as the height direction of the door impact beam 10. Note that the height direction of the door impact beam 10 may differ from the vehicle height direction of the automobile 1.

[0049] The second plate portion 22 is connected to one side portion 21 a of the first plate portion 21 via a ridge portion 221. In other words, the connection portion between the side portion 21 a of the first plate portion 21 and the side portion 22 a of the second plate portion 22 forms the ridge portion 221. The third plate portion 23 is connected to the other side portion 21 b of the first plate portion 21 via a ridge portion 231. In other words, the connection portion between the side portion 21 b of the first plate portion 21 and the side portion 23 a of the third plate portion 23 forms the ridge portion 231. The ridge portions 221 and 231 each have a substantially arc shape when viewed in cross section of the beam main body 20.

[0050] In this embodiment, the first plate portion 21, the second plate portion 22, and the third plate portion 23 are each flat. However, the shape of each of the plate portions 21 to 23 is not limited to this. Each of the plate portions 21 to 23 may have, for example, a curved portion or a recess extending in the longitudinal direction.

[0051] The first side flange 24 is connected to a side portion 22b of the second plate portion 22 opposite the first plate portion 21 via a ridge portion 222. In other words, the connection portion between the side portion 22b of the second plate portion 22 and the side portion of the first side flange 24 forms the ridge portion 222. The first side flange 24 protrudes from the second plate portion 22 on the side opposite the first plate portion 21 in the width direction.

[0052] The second side flange portion 25 is connected to a side portion 23b of the third plate portion 23 opposite to the first plate portion 21 via a ridge portion 232. In other words, the connection portion between the side portion 23b of the third plate portion 23 and the side portion of the second side flange portion 25 forms the ridge portion 232. The second side flange portion 25 protrudes from the third plate portion 23 in the width direction opposite to the first plate portion 21. The ridge portions 222 and 232 each have a substantially arc shape when viewed in cross section of the beam body 20.

[0053] In this embodiment, the continuous flange portions 30, 40 are provided at both ends of the door impact beam 10. Specifically, the continuous flange portion 30 is connected to the front end of the beam main body 20 in the longitudinal direction, and the continuous flange portion 40 is connected to the rear end of the beam main body 20 in the longitudinal direction.

[0054] The door impact beam 10 is joined to the door body 4 (FIG. 2) via continuous flange portions 30, 40 provided at both ends. In other words, the continuous flange portions 30, 40 serve as a joining surface with the door body 4. The method for joining the door impact beam 10 to the door body 4 is not particularly limited, but may be welding, for example. Arc welding or laser welding may be used as the welding method.

[0055] There are no particular limitations on the shapes of the continuous flange portions 30, 40. For example, the continuous flange portions 30, 40 each have a shape corresponding to the mounting portion of the door body 4 (FIG. 2) to which they are joined.

[0056] An example of the shape of the continuous flange portions 30, 40 will be described using Figures 3 and 4. Referring to Figure 3, the continuous flange portion 30 includes a first end flange portion 31, a second end flange portion 32, and a third end flange portion 33. The first end flange portion 31 is connected to the front end portion 21c of the first plate portion 21 in the longitudinal direction. In this embodiment, the first end flange portion 31 protrudes forward in the longitudinal direction from the first plate portion 21. The width of the first end flange portion 31 is the same as the width of the entire beam main body 20. Therefore, the width of the first end flange portion 31 is greater than the width of the first plate portion 21.

[0057] The second end flange portion 32 is connected to the longitudinal front end portion 22c of the second plate portion 22 via a ridge portion 322. In other words, the connection portion between the second end flange portion 32 and the end portion 22c of the second plate portion 22 forms the ridge portion 322. The second end flange portion 32 is inclined with respect to the longitudinal direction. Therefore, the second end flange portion 32 exists on a different plane from the first end flange portion 31. In this embodiment, the second end flange portion 32 intersects with the longitudinal direction. The second end flange portion 32 protrudes from the second plate portion 22 on the opposite side from the first plate portion 21 in the width direction. The second end flange portion 32 is disposed at a right angle to the second plate portion 22. However, the angle of the second end flange portion 32 with respect to the second plate portion 22 does not have to be a right angle.

[0058] The third end flange 33 is connected to the longitudinal front end 23c of the third plate 23 via a ridge 332. In other words, the connection between the third end flange 33 and the end 23c of the third plate 23 forms the ridge 332. The third end flange 33 is inclined with respect to the longitudinal direction. Therefore, the third end flange 33 exists on a different plane from the first end flange 31. In this embodiment, the third end flange 33 intersects with the longitudinal direction. The third end flange 33 protrudes from the third plate 23 on the opposite side from the first plate 21 in the width direction. The third end flange 33 is disposed perpendicular to the third plate 23. However, the angle of the third end flange 33 relative to the third plate 23 does not have to be a right angle.

[0059] The second end flange portion 32 and the third end flange portion 33 are each continuous with the first end flange portion 31, and the end flange portions 31-33 form a continuous flange portion 30. In this case, the first end flange portion 31, the second end flange portion 32, and the third end flange portion 33 are not separated. The continuous flange portion 30 has an L-shape in a side view of the door impact beam 10. A ridge-like connecting portion 321 is formed between the second end flange portion 32 and the first end flange portion 31, which are continuous with each other. A ridge-like connecting portion 331 is formed between the third end flange portion 33 and the first end flange portion 31, which are continuous with each other. The connecting portion 321 and the connecting portion 331 each have a substantially arc shape in a side view of the door impact beam 10. The angle formed between the second end flange portion 32 and the first end flange portion 31 and the angle formed between the third end flange portion 33 and the first end flange portion 31 are, for example, greater than or equal to 90° and less than or equal to 135°. These angles may be less than or equal to 120°.

[0060] Furthermore, the second end flange portion 32 is continuous with the first side flange portion 24. A ridge portion 323 is formed between the second end flange portion 32 and the first side flange portion 24, which are continuous with each other. Similarly, the third end flange portion 33 is continuous with the second side flange portion 25. A ridge portion 333 is formed between the third end flange portion 33 and the second side flange portion 25, which are continuous with each other. The ridge portions 323 and 333 each have a substantially arc shape when the door impact beam 10 is viewed from the side.

[0061] 4 , the continuous flange portion 40 includes a first end flange portion 41, a second end flange portion 42, and a third end flange portion 43. The first end flange portion 41 is connected to the longitudinal rear end portion 21d of the first plate portion 21 via a ridge portion 411. In other words, the connection portion between the first end flange portion 41 and the end portion 21d of the first plate portion 21 forms the ridge portion 411. In this embodiment, the first end flange portion 41 is inclined with respect to the longitudinal direction. Specifically, the first end flange portion 41 protrudes from the first plate portion 21 on the opposite side to the second plate portion 22 and the third plate portion 23 in the height direction. The first end flange portion 41 intersects with the longitudinal direction.

[0062] The second end flange portion 42 is connected to the rear end 22d of the second plate portion 22 in the longitudinal direction via a ridge portion 421. In other words, the connection between the second end flange portion 42 and the end 22d of the second plate portion 22 forms the ridge portion 421. The second end flange portion 42 is inclined with respect to the longitudinal direction. In this embodiment, the second end flange portion 42 is on the same plane as the first end flange portion 41. In other words, the second end flange portion 42 intersects with the longitudinal direction. The second end flange portion 42 protrudes from the second plate portion 22 on the side opposite to the first plate portion 21 in the width direction. The second end flange portion 42 is disposed at a right angle to the second plate portion 22. However, the angle of the second end flange portion 42 with respect to the second plate portion 22 does not have to be a right angle.

[0063] The third end flange 43 is connected to the rear end 23d of the third plate 23 in the longitudinal direction via a ridge 431. In other words, the connection between the third end flange 43 and the end 23d of the third plate 23 forms the ridge 431. The third end flange 43 is inclined with respect to the longitudinal direction. In this embodiment, the third end flange 43 is on the same plane as the first end flange 41 and the second end flange 42. In other words, the third end flange 43 intersects with the longitudinal direction. The third end flange 43 protrudes from the third plate 23 on the opposite side to the first plate 21 in the width direction. The third end flange 43 is disposed perpendicular to the third plate 23. However, the angle of the third end flange 43 relative to the third plate 23 does not have to be a right angle.

[0064] The second end flange portion 42 and the third end flange portion 43 are each continuous with the first end flange portion 41, and the end flange portions 41 to 43 form a continuous flange portion 40. In this case, the first end flange portion 41, the second end flange portion 42, and the third end flange portion 43 are not separated. The continuous flange portion 40 is flat.

[0065] The second end flange portion 42 is continuous with the first side flange portion 24. A ridge portion 422 is formed between the second end flange portion 42 and the first side flange portion 24, which are continuous with each other. Similarly, the third end flange portion 43 is continuous with the second side flange portion 25. A ridge portion 432 is formed between the third end flange portion 43 and the second side flange portion 25, which are continuous with each other. The ridge portions 422 and 432 each have a substantially arc shape when the door impact beam 10 is viewed from the side.

[0066] The door impact beam 10 can be manufactured by, for example, pressing a metal plate. The pressing may be cold pressing or hot pressing (hot stamping). The metal plate is, but is not limited to, a steel plate.

[0067] At least a portion of the door impact beam 10 may be composed of a plate-shaped surface-softened portion 50. An example in which the entire beam body 20 is composed of the surface-softened portion 50 will be described below. However, the continuous flange portions 30, 40 may also be composed of the surface-softened portion 50. Alternatively, only a portion of the beam body 20 and / or the continuous flange portions 30, 40 may be composed of the surface-softened portion 50. The surface-softened portion 50 is preferably provided in a portion of the beam body 20 and / or the continuous flange portions 30, 40 that is particularly prone to cracking. The surface-softened portion 50 is preferably provided in the longitudinal center of the beam body 20. In this case, the collision resistance of the door impact beam 10 can be improved, particularly in side collisions.

[0068] As described above, with reference to FIG. 5 , the beam body 20 is formed from the surface-softened portion 50. The Vickers hardness of the surface 50 a of the surface-softened portion 50 is lower than the Vickers hardness at the center of the surface-softened portion 50 in the thickness direction. The Vickers hardness of the surface 50 a of the surface-softened portion 50 is, for example, 100 HV or more lower than the Vickers hardness at the center of the surface-softened portion 50 in the thickness direction. This improves the bending deformability of the surface-softened portion 50 (beam body 20), making it easier for the surface-softened portion 50 to absorb impacts. Examples of upper limits for the difference between the Vickers hardness of the surface 50 a of the surface-softened portion 50 and the Vickers hardness at the center of the surface-softened portion 50 in the thickness direction include 250 HV, 300 HV, 350 HV, 400 HV, 500 HV, 550 HV, 600 HV, and 650 HV.

[0069] If the Vickers hardness of the surface 50a of the surface-softened portion 50 is 0.5 times or more the Vickers hardness at the center of the surface-softened portion 50 in the plate thickness direction, the load-bearing capacity during a collision can be improved, particularly in the later stage of the stroke during a collision. More preferably, the Vickers hardness of the surface 50a of the surface-softened portion 50 is 0.6 times or more the Vickers hardness at the center of the surface-softened portion 50 in the plate thickness direction. On the other hand, if the Vickers hardness of the surface 50a of the surface-softened portion 50 is less than 0.9 times the Vickers hardness at the center of the surface-softened portion 50 in the plate thickness direction, the deformability of the surface-softened portion 50 can be sufficiently improved. More preferably, the Vickers hardness of the surface 50a of the surface-softened portion 50 is less than 0.8 times the Vickers hardness at the center of the surface-softened portion 50 in the plate thickness direction.

[0070] The Vickers hardness of the surface-softened portion 50 at the center of the thickness direction is measured as follows. A cross section perpendicular to the plate surface of a sample cut from the surface-softened portion 50 is taken, and the sample is prepared for hardness testing. The measurement surface is prepared in accordance with JIS Z 2244:2020. The measurement surface is polished using #600 to #1500 silicon carbide paper, and then polished to a mirror finish using a liquid in which diamond powder with a particle size of 1 μm to 6 μm is dispersed in a diluted solution such as alcohol or pure water. The hardness test is performed in accordance with JIS Z 2244:2020. Using a micro-Vickers hardness tester, 10 indentations are measured at the center of the thickness direction of the sample with a test force of 1 kgf, with a center-to-center distance of at least three times the average diagonal length of the indentations. The Vickers hardness calculated from the average value of the measured values ​​is set as the Vickers hardness at the center in the thickness direction of the surface-softened portion 50.

[0071] The Vickers hardness of the surface 50a of the surface-softened portion 50 is measured on a cross section obtained by cutting the surface-softened portion 50 along the plate thickness direction in accordance with the Vickers hardness test described in JIS Z 2244:2020.

[0072] After the above cross section is subjected to sample preparation of the measurement surface, it is subjected to a hardness test. The measurement surface is prepared so that the surface has as little unevenness as possible and no sagging occurs near the surface in order to accurately measure the Vickers hardness near the surface of the sample. Here, the measurement surface is sputtered with an argon ion beam using a cross-section polisher manufactured by JEOL. At this time, in order to prevent streaky unevenness from occurring on the measurement surface, an argon ion beam is irradiated from 360 degrees on the measurement surface using a sample rotation holder manufactured by JEOL.

[0073] The Vickers hardness of the sample with the prepared measurement surface is measured using a micro Vickers hardness tester. The measurement point is located 20 μm thick from the surface 50 a of the surface-softened portion 50. If a plating layer is present in the surface-softened portion 50, the measurement point is located 20 μm thick from the surface of the steel sheet base material directly below the plating layer. If an alloy layer is present between the plating layer and the steel sheet base material in addition to the plating layer in the surface-softened portion 50, the measurement point is located 20 μm thick from the surface of the steel sheet base material directly below the alloy layer. Ten indentations are measured at the above-mentioned thickness positions from the surface of the sample in a direction perpendicular to the surface (sheet thickness direction) with a test force of 10 gf, with a center-to-center distance of at least three times the average diagonal length of the indentations. The Vickers hardness calculated from the average of the measured values ​​is the Vickers hardness of the surface 50 a of the surface-softened portion 50.

[0074] [Effects] The door impact beam 10 according to this embodiment has continuous flange portions 30, 40 at both longitudinal ends. In the continuous flange portion 30, the second end flange portion 32 and the third end flange portion 33 are each inclined relative to the longitudinal direction. In the continuous flange portion 40, the first end flange portion 41, the second end flange portion 42, and the third end flange portion 43 are each inclined relative to the longitudinal direction. By joining each continuous flange portion 30, 40 to the door body 4 constituting the side door, the continuous flange portions 30, 40, which form the joint surface with the door body 4, are continuous, thereby increasing the joint surface area. This allows for the load generated by a frontal collision to be distributed. Therefore, the door impact beam 10 according to this embodiment can ensure high crashworthiness against a frontal collision. The increased crashworthiness allows for a thinner plate, thereby reducing the weight of the door impact beam 10. As a result, both crashworthiness and weight reduction can be achieved.

[0075] The beam body 20 of the door impact beam 10 according to this embodiment has a hat-shaped cross section. A ridgeline 221 is provided between the first plate portion 21 and the second plate portion 22, and a ridgeline 231 is provided between the first plate portion 21 and the third plate portion 23. Therefore, the door impact beam 10 according to this embodiment can ensure higher crash resistance. Furthermore, a ridgeline 222 is provided between the second plate portion 22 and the first side flange portion 24, and a ridgeline 232 is provided between the third plate portion 23 and the second side flange portion 25. This further improves the crash resistance of the door impact beam 10.

[0076] [Second embodiment] Fig. 6 is a cross-sectional view of the beam body 20 of a door impact beam according to a second embodiment. In this embodiment, as shown in Fig. 6, the surface-softened portion 50 is formed of a hardened portion 51 and a softened portion 52.

[0077] The hardened portion 51 includes the central portion in the thickness direction of the surface-softened portion 50 (beam body 20). The softened portion 52 is laminated on the hardened portion 51. The softened portion 52 is provided, for example, on both sides of the hardened portion 51 in the thickness direction. The softened portions 52 are respectively arranged along the surface 50a on both sides of the surface-softened portion 50 in the thickness direction. In this case, the hardened portion 51 is arranged between the softened portions 52. However, the softened portion 52 may be provided on only one side of the hardened portion 51 in the thickness direction.

[0078] The thickness of the softened portion 52 is preferably 80 μm or more from the viewpoint of ensuring sufficient strength of the surface-softened portion 50. The thickness of the softened portion 52 may be 200 μm or less. Furthermore, the thickness of the softened portion 52 may be 5% or more and 20% or less of the plate thickness of the surface-softened portion 50. If the thickness of the softened portion 52 is 20% or less of the plate thickness of the surface-softened portion 50, the ratio of the volume of the softened portion 52 to the volume of the surface-softened portion 50 is small, and therefore the load-bearing capacity of the surface-softened portion 50 can be ensured. The thickness of the softened portion 52 is preferably 17% or less of the thickness of the surface-softened portion 50, and more preferably 14% or less. On the other hand, when the softened portion 52 is provided over the entire surface 50a of the surface-softened portion 50, the deformability of the softened portion 52 can be fully exhibited if the thickness of the softened portion 52 is 80 μm or more and 5% or more of the plate thickness of the surface-softened portion 50. It is more preferable that the thickness of the softened portion 52 be 8% or more of the plate thickness of the surface-softened portion 50.

[0079] The hardened portion 51 has a constant Vickers hardness in the plate thickness direction. The Vickers hardness of the hardened portion 51 is preferably 400 HV or higher. When the Vickers hardness of the hardened portion 51 is 400 HV or higher, the deformability of the surface-softened portion 50 is likely to be significantly improved. The Vickers hardness of the hardened portion 51 is more preferably 500 HV or higher, and even more preferably 600 HV or higher. The Vickers hardness of the hardened portion 51 may be 700 HV or higher. There is no particular upper limit to the Vickers hardness of the hardened portion 51, but in consideration of formability, etc., it is preferably 900 HV or lower, and more preferably 800 HV or lower. Examples of the lower limit of the Vickers hardness of the hardened portion 51 include 500 HV, 550 HV, 600 HV, 700 HV, 720 HV, and 750 HV. Examples of upper limits of the Vickers hardness of the hardened portion 51 include 1100 HV, 1050 HV, 1000 HV, 950 HV, 900 HV, 850 HV, and 800 HV. The Vickers hardness of the hardened portion 51 may be 350 HV or more and 770 HV or less.

[0080] The Vickers hardness of the softened portion 52 varies in the thickness direction. Specifically, the Vickers hardness of the softened portion 52 gradually decreases from the center side in the thickness direction of the surface-softened portion 50 toward the surface 50a side. In other words, the Vickers hardness of the softened portion 52 is smallest at the surface 50a of the surface-softened portion 50.

[0081] The position of the boundary between the softened portion 52 and the hardened portion 51 can be measured as follows. A cross section perpendicular to the plate surface of the sample cut from the surface-softened portion 50 is taken, and the sample surface to be measured is prepared and used for a hardness test. The measurement surface is prepared so that irregularities are minimized and sagging near the surface is prevented in order to accurately measure the Vickers hardness near the surface of the sample. Here, the measurement surface is sputtered with an argon ion beam using a cross-section polisher manufactured by JEOL Ltd. At this time, in order to prevent streaky irregularities from occurring on the measurement surface, an argon ion beam is irradiated from 360 degrees using a sample rotating holder manufactured by JEOL Ltd.

[0082] The Vickers hardness of the sample with the prepared measurement surface is measured using a micro Vickers hardness tester. The area from the surface of the sample corresponding to the softened portion 52 of the sample is measured in a direction perpendicular to the surface (thickness direction) with a test force of 50 gf.

[0083] Measurements are performed from the surface side of the sample to the center in the sheet thickness direction. The measurement position on the most surface side of the sample is 20 μm thick from the surface 50a of the surface-softened portion 50. If a plating layer is present in the surface-softened portion 50, the measurement position is 20 μm thick from the surface of the steel sheet base material directly below the plating layer. If an alloy layer is present between the plating layer and the steel sheet base material in addition to the plating layer in the surface-softened portion 50, the measurement position is 20 μm thick from the surface of the steel sheet base material directly below the alloy layer. Measurement points are spaced at equal intervals of 5 μm to 15 μm in the sheet thickness direction, and the distance between the centers of the indentations is at least three times the average diagonal length of the indentations. Depending on the average diagonal length of the indentations, it may not be possible to ensure a center-to-center distance of at least three times the average diagonal length of the indentations in a row along the sheet thickness direction. In this case, measurements are performed at different positions in the sheet thickness direction while varying the positions perpendicular to the sheet thickness direction. This makes it possible to satisfy the measurement conditions that the depressions are spaced at equal intervals of 5 μm to 15 μm in the thickness direction and the distance between the centers of the depressions is at least three times the average diagonal length of the depressions.

[0084] Then, a slope Δbi obtained from the Vickers hardness at three consecutive points among the measurement points is calculated. The slope Δbi is calculated using the following formula (1). where, Δbi: gradient (HV / μm) calculated from the three points i to i+2; xi: thickness position (μm) of the i-th measurement point from the surface 50a of the surface-softened portion 50; xk: thickness position (μm) from the surface 50a of the surface-softened portion 50; yk: average value (HV) of Vickers hardness at three different points at the thickness position xk.

[0085] Of the three measurement points at which the slope Δbi calculated by equation (1) from the surface 50a side of the surface softened portion 50 first becomes 0.5 (HV / μm) or less, the thickness position of the measurement point closest to the surface 50a is determined to be the boundary position between the softened portion 52 and the hardened portion 51.

[0086] Fig. 7 is a partially enlarged view of Fig. 6. As shown in Fig. 7, the softened portion 52 preferably includes a first region A1 and a second region A2. The first region A1 is a region from the surface 50a of the surface-softened portion 50 to 40% of the thickness of the softened portion 52. The second region A2 is a region of the softened portion 52 excluding the first region A1. In other words, the second region A2 is a region from 40% to 100% of the thickness of the softened portion 52.

[0087] The thickness of the first region A1 is, for example, 32 μm or more and 80 μm or less. When the thickness of the softened portion 52 is 80 μm, the second region A2 exists in a thickness range of 32 μm or more and 80 μm or less from the surface 50 a of the surface-softened portion 50 (a thickness range of 48 μm). When the thickness of the softened portion 52 is 200 μm, the second region A2 exists in a thickness range of 80 μm or more and 200 μm or less from the surface 50 a of the surface-softened portion 50 (a thickness range of 120 μm).

[0088] The absolute value ΔHV1 of the hardness change in the plate thickness direction in the first region A1 is preferably larger than the absolute value ΔHV2 of the hardness change in the plate thickness direction in the second region A2. If ΔHV1 is larger than ΔHV2, the collision resistance performance of the surface-softened portion 50 is improved. The method of calculating ΔHV1 and ΔHV2 will be described later.

[0089] The absolute value ΔHV1 of the hardness change in the first region A1 is preferably 100 HV or more and less than 200 HV. If ΔHV1 is 100 HV or more, stress concentration during bending deformation of the surface-softened portion 50 can be alleviated, thereby improving bending characteristics. Furthermore, if ΔHV1 is less than 200 HV, the effect of alleviating stress concentration during bending deformation of the surface-softened portion 50 is further enhanced, resulting in better bending characteristics. Therefore, when ΔHV1 is 100 HV or more and less than 200 HV, good bending characteristics can be obtained, and the deformability of the surface-softened portion 50 is improved. Specifically, the load drop immediately after the load peak can be made gentler in the later stroke of a collision. ΔHV1 may be less than 300 HV or less than 400 HV.

[0090] The Vickers hardness of the first region A1 and the second region A2 is measured as follows. A cross section perpendicular to the plate surface of the sample cut from the surface-softened portion 50 is taken, and the sample surface is prepared for hardness testing. The preparation of the measurement surface is carried out to minimize unevenness and prevent sagging near the surface in order to accurately measure the Vickers hardness near the surface of the sample. Here, the measurement surface is sputtered with an argon ion beam using a cross-section polisher manufactured by JEOL Ltd. At this time, to prevent streaky unevenness from occurring on the measurement surface, an argon ion beam is irradiated from 360 degrees on the measurement surface using a sample rotating holder manufactured by JEOL Ltd.

[0091] The Vickers hardness of the sample with the prepared measurement surface is measured using a micro Vickers hardness tester. The area from the surface of the sample corresponding to the softened portion 52 of the sample is measured in a direction perpendicular to the surface (thickness direction) with a test force of 10 gf. The Vickers hardness measurement results of the first area A1 and the second area A2 are used to calculate ΔHV1 and ΔHV2, as described below. The number of measurement points for calculating ΔHV1 and ΔHV2 varies depending on the thickness of the sample and is set in accordance with the description of JIS Z 2244:2020.

[0092] The measurement position on the surface-most side of the sample is 20 μm thick from the surface 50 a of the surface-softened portion 50. If a plating layer is present in the surface-softened portion 50, the measurement position is 20 μm thick from the surface of the steel sheet base material directly below the plating layer. If an alloy layer is present between the plating layer and the steel sheet base material in addition to the plating layer in the surface-softened portion 50, the measurement position is 20 μm thick from the surface of the steel sheet base material directly below the alloy layer. This measurement point is different from the measurement point used for measuring the Vickers hardness of the surface 50 a of the surface-softened portion 50 described above. When measuring the Vickers hardness of the first region A1, the indentations are measured at at least two locations in the thickness direction, at equal intervals of 15 μm or less in the thickness direction and with a center-to-center distance of at least three times the average diagonal length of the indentations. Depending on the average diagonal length of the indentations, it may be possible to measure only one point in a row along the thickness direction for the first region A1. In this case, the Vickers hardness is measured at at least two points in the first region A1, while varying the positions in the direction perpendicular to the thickness direction and varying the positions in the thickness direction, so that the Vickers hardness is measured at at least two points in the first region A1, while satisfying the measurement conditions of equal intervals of 15 μm or less in the thickness direction and the distance between the centers of the indentations being three times or more the average diagonal length of the indentations.

[0093] The Vickers hardness of the second region A2 is measured within the softened portion 52, excluding the first region A1. When measuring the Vickers hardness of the second region A2, the dimples are measured at at least two locations in the thickness direction, at equal intervals of 15 μm or less in the thickness direction and with a center-to-center distance of at least three times the average diagonal length of the dimples. Depending on the average diagonal length of the dimples, it may not be possible to measure two adjacent points at the specified interval in a row along the thickness direction for the second region A2. In this case, measurements are performed at different positions in the thickness direction while varying the positions perpendicular to the thickness direction. This allows the Vickers hardness of the second region A2 to be measured while satisfying the measurement conditions of equal intervals of 15 μm or less in the thickness direction and a center-to-center distance of at least three times the average diagonal length of the dimples. The second region A2 may be measured in the same row as the first region A1. The second region A2 may be measured at a total of four points, for example, one point near the boundary between the first region A1 and the second region A2, one point near the boundary between the softened portion 52 and the hardened portion 51, and two points between these two points. If the second region A2 exists up to a position 200 μm from the surface 50 a, the measurement points for the first region A1 and the second region A2 are, for example, 20 μm, 35 μm, 50 μm, 65 μm, 80 μm, 95 μm, 110 μm, 125 μm, 140 μm, 155 μm, 170 μm, 185 μm, and 200 μm from the surface 50 a.

[0094] When the softened portion 52 is provided on both sides of the hardened portion 51 in the thickness direction, the same measurement is also performed on the opposite surface 50a of the sample.

[0095] ΔHV1 is calculated by the following procedure: After measuring the Vickers hardness of the first region A1, the hardness gradient Δa of the first region A1 is calculated from all measurement points included in the first region A1 of the sample cut out from the surface-softened portion 50 using the following formula (2). Here, Δa: gradient of hardness change in the thickness direction in the first region A1 (HV / %); ai: proportion (%) of the distance from the surface at the i-th measurement point to the total thickness of the softened portion 52; ci: average value (HV) of Vickers hardness at three different points at the i-th measurement thickness position; n: sum of all measurement points included in the first region A1.

[0096] When the softened portion 52 is provided on both sides of the hardened portion 51 in the thickness direction, the gradient Δa1 on one surface 50a side is calculated from equation (2), and then the gradient Δa2 on the other surface 50a side is calculated from equation (2). The arithmetic mean of Δa1 and Δa2 can be set to Δa.

[0097] ΔHV1 can be obtained by multiplying Δa obtained by equation (2) by the ratio of the thickness of the first region A1 to the entire thickness of the softened portion 52.

[0098] ΔHV2 is calculated by the following procedure: After measuring the Vickers hardness of the second region A2, the hardness gradient ΔA of the second region A2 is calculated from all measurement points included in the second region A2 of the sample cut out from the surface-softened portion 50 using the following formula (3). where, ΔA: gradient of hardness change in the plate thickness direction in the second region A2 (HV / %); Ai: proportion (%) of the distance from the surface at the i-th measurement point to the total thickness of the softened portion 52; Ci: average value (HV) of Vickers hardness at three different points at the i-th measurement thickness position; N: sum of all measurement points included in the second region A2.

[0099] When the softened portion 52 is provided on both sides of the hardened portion 51 in the thickness direction, the gradient ΔA1 on one surface 50a side is calculated from the formula (3), and then the gradient ΔA2 on the other surface 50a side is calculated from the formula (3). The arithmetic mean of ΔA1 and ΔA2 can be set as ΔA.

[0100] ΔHV2 can be obtained by multiplying ΔA obtained by equation (3) by the ratio of the thickness of the second region A2 to the entire thickness of the softened portion 52.

[0101] There are no particular limitations on the method for forming the softened portion 52 in the surface-softened portion 50. The softened portion 52 is formed, for example, by reducing the carbon content of a portion of the blank that is the material for the surface-softened portion 50 that will become the softened portion 52 (near the surface of the blank) to be less than the carbon content of a portion of the blank that will become the hardened portion 51.

[0102] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure.

[0103] [Modifications] In the above embodiment, the beam body 20 of the door impact beam 10 has a hat-shaped cross section. However, the shape of the beam body 20 is not limited to this. FIGS. 8 and 9 are cross-sectional views of modifications of the beam body 20. In the example shown in FIG. 8 , the cross-sectional shape of the beam body 20 is L-shaped. In this case, the beam body 20 is composed of a first plate portion 21, a second plate portion 22, and a ridge portion 221 provided between them. In the example shown in FIG. 9 , the cross-sectional shape of the beam body 20 is U-shaped. In this case, the beam body 20 is composed of a first plate portion 21, a second plate portion 22, a third plate portion 23, a ridge portion 221 provided between the first plate portion 21 and the second plate portion 22, and a ridge portion 231 provided between the first plate portion 21 and the third plate portion 23. However, the cross-sectional shape of the beam body 20 may be other shapes.

[0104] In the above embodiment, the second end flange portion 32 and the third end flange portion 33 of the continuous flange portion 30 each protrude outward in the width direction of the door impact beam 10. Specifically, the second end flange portion 32 protrudes from the second plate portion 22 on the side opposite the first plate portion 21 in the width direction. The third end flange portion 33 protrudes from the third plate portion 23 on the side opposite the first plate portion 21 in the width direction. However, the direction in which the second end flange portion 32 and the third end flange portion 33 protrude is not particularly limited as long as they are inclined with respect to the longitudinal direction. In other words, the second end flange portion 32 and the third end flange portion 33 may each protrude in any direction except along the longitudinal direction. The second end flange portion 32 and the third end flange portion 33 may each protrude inward in the width direction of the door impact beam 10. The same applies to the continuous flange portion 40 as to the continuous flange portion 30.

[0105] In the door impact beam 10 of the above embodiment, the continuous flange portions 30, 40 are provided at both longitudinal ends thereof. However, the continuous flange portion may be provided at only one end of the door impact beam 10.

[0106] In the above embodiment, the door impact beam 10 (the first door impact beam 10a and the second door impact beam 10b) is supported only at both ends. However, the portion of the door impact beam 10 between the both ends may be supported by a single or multiple support members. The support members are provided in the inner region of the edge of the door body 4. The support members may be joined to, for example, the outer panel of the side door (front door 2) or to other members.

[0107] In the above embodiment, the second end flange portions 32, 42 and the third end flange portions 33, 43 of the door impact beam 10, which are joined to the door body 4, are substantially parallel to the width direction. However, as shown in Figures 10 and 11, the second end flange portions 32, 42 and the third end flange portions 33, 43 may be inclined with respect to the width direction.

[0108] To confirm the effects of the present disclosure, a side door (front door 2) equipped with the door impact beams 10a, 10b according to the above embodiment was analyzed using commercially available structural analysis software (LS-DYNA, manufactured by Livermore Software Technology Corporation). Specifically, an analytical model of the front door 2 shown in FIG. 2 was created, and an impactor was inserted into the front door 2 from the front to the rear. The load (reaction force) generated on the impactor and the stroke (displacement) of the impactor were then investigated.

[0109] In this example, two analytical models, Examples 1 and 2, were created. In both Examples 1 and 2, the door impact beams 10a and 10b each had a continuous flange at both ends. In Example 1, the door impact beams 10a and 10b had a thickness of 1.4 mm and a tensile strength of 1.5 GPa. In Example 2, the door impact beams 10a and 10b had the same thickness as in Example 1 and a tensile strength of 2.0 GPa.

[0110] As a comparative example, an analytical model was also created for a front door having a different configuration from the front door 2 described above, and analysis was performed in the same manner as in Examples 1 and 2. Each door impact beam in the comparative example did not have a continuous flange portion at any end. That is, in each door impact beam in the comparative example, the first end flange portion, the second end flange portion, and the third end flange portion were not continuous but were separated from each other. The other conditions of the comparative example were the same as those of Example 1.

[0111] 12 and 13 summarize the results of this example. In FIG. 12, the vertical axis represents load, and the horizontal axis represents stroke. In FIG. 13, the vertical axis represents load per unit weight, and the horizontal axis represents stroke. The area of ​​the graphs in FIGS. 12 and 13 represents the absorbed energy of the front door. The results shown in FIG. 12 indicate that the absorbed energy of the front door in Examples 1 and 2 was significantly improved compared to the comparative example. Furthermore, the results shown in FIG. 13 indicate that the absorbed energy per unit weight of the front door in Examples 1 and 2 was also significantly improved compared to the comparative example. From these results, the front door 2 equipped with the door impact beams 10a and 10b according to the above embodiment can efficiently absorb frontal collision loads, thereby suppressing deformation toward the interior of the vehicle. Therefore, it can be seen that this front door 2 has excellent crashworthiness in frontal collisions.

[0112] DESCRIPTION OF SYMBOLS 10, 10a, 10b: Door impact beam 1: Automobile 2: Front door 4: Door body 4b: Door hinge portion 4c: Front edge portion 20: Beam body 21: First plate portion 21a, 21b: Side portion 21c, 21d: End portion 22: Second plate portion 22a, 22b: Side portion 22c, 22d: End portion 221, 222: Ridge portion 23: Third plate portion 23a, 23b: Side portion 23c, 23d: End portion 231, 232: Ridge portion 24: First side flange portion 25: Second side flange portion 30, 40: Continuous flange portion 31, 41: First end flange portion 32, 42: Second end flange portion 33, 43: Third end flange portion 50: Surface-softened portion 50a: Surface 51: Hardened portion 52: Softened portion A1: First region A2: Second region

Claims

1. A door impact beam used for a side door of an automobile, comprising: a first plate portion extending in the longitudinal direction of the door impact beam; a second plate portion extending in the longitudinal direction and connected to one side portion of the first plate portion via a ridge line portion; a first end flange portion connected to an end portion of the first plate portion in the longitudinal direction; and a second end flange portion connected to an end portion of the second plate portion in the longitudinal direction, the second end flange portion being inclined with respect to the longitudinal direction and continuous with the first end flange portion.

2. The door impact beam according to claim 1, wherein the first plate portion and the second plate portion are each flat.

3. The door impact beam according to claim 1, wherein the second end flange portion lies on the same plane as the first end flange portion.

4. The door impact beam according to claim 1, wherein the second end flange portion lies on a plane different from that of the first end flange portion.

5. The door impact beam according to claim 1, further comprising: a first side flange portion extending in the longitudinal direction and connected to the side portion of the second plate portion opposite to the first plate portion via a ridge line portion, the first side flange portion being continuous with the second end flange portion; and a ridge line portion is formed between the second end flange portion and the first side flange portion.

6. The door impact beam according to claim 1, further comprising: a third plate portion extending in the longitudinal direction and connected to the other side portion of the first plate portion via a ridge line portion; and a third end flange portion connected to an end portion of the third plate portion, the third end flange portion being inclined with respect to the longitudinal direction and continuous with the first end flange portion.

7. The door impact beam according to claim 6, further comprising: a second side flange portion extending in the longitudinal direction and connected to the side portion of the third plate portion opposite to the first plate portion via a ridge line portion, the second side flange portion being continuous with the third end flange portion; and a ridge line portion is formed between the third end flange portion and the second side flange portion.

8. The door impact beam according to claim 1, wherein the first end flange portion and the second end flange portion are provided at both ends of the door impact beam respectively.

9. The door impact beam according to claim 1, wherein the first end flange portion and the second end flange portion are provided only at one end of the door impact beam respectively.

10. The door impact beam according to claim 1, wherein at least a part of the door impact beam is composed of a plate-shaped surface softening portion, and the Vickers hardness of the surface of the surface softening portion is smaller than the Vickers hardness at the center in the plate thickness direction of the surface softening portion.

11. The door impact beam according to claim 10, wherein the surface softening portion is formed by a hardening portion and a softening portion laminated on the hardening portion, the Vickers hardness at the center in the plate thickness direction of the surface softening portion is 400 HV or more, the thickness of the softening portion is 80 μm or more and 5% or more and 20% or less of the plate thickness of the surface softening portion, the Vickers hardness of the surface of the surface softening portion is 0.5 times or more and less than 0.9 times the Vickers hardness at the center in the plate thickness direction of the surface softening portion, the softening portion includes a first region which is a region from the surface of the surface softening portion to 40% of the thickness of the softening portion and a second region which is a region of the softening portion excluding the first region, and the absolute value ΔHV1 of the change in the Vickers hardness in the plate thickness direction in the first region is larger than the absolute value ΔHV2 of the change in the Vickers hardness in the plate thickness direction in the second region.

12. A side door of an automobile, comprising a door body and the door impact beam according to any one of claims 1 to 11 joined to the door body.

13. The side door according to claim 12, wherein the door body includes a door hinge portion, and the first end flange portion and the second end flange portion are joined to the door hinge portion respectively.

14. The side door according to claim 12, wherein the first end flange portion and the second end flange portion are joined to the front edge portion of the door body respectively.

15. The side door according to claim 12, wherein the side door is the front door of the motor vehicle.

16. A motor vehicle comprising a side door including a door body and the door impact beam according to any one of claims 1 to 11 joined to the door body.

17. The motor vehicle according to claim 16, wherein the door body includes a door hinge portion, and the first end flange portion and the second end flange portion are each joined to the door hinge portion.

18. The motor vehicle according to claim 16, wherein the first end flange portion and the second end flange portion are each joined to the front edge portion of the door body.

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