Side door of automobile and automobile

Abstract

This side door (10) of an automobile comprises a door body (11), a first door impact beam (20a), a second door impact beam (20b), and an inclined member (14). The second door impact beam (20b) is shorter than the first door impact beam (20a). The second door impact beam (20b) is disposed in a position lower than the first door impact beam (20a) in the vehicle height direction of the automobile. The inclined member (14) is connected to a front edge portion (11c) or a rear edge portion (11e) of the door body (11). The inclined member (14) is inclined with respect to the vehicle length direction and the vehicle height direction. When the inclined member (14) is connected to the front edge portion (11c), the front end of the second door impact beam (20b) is connected to the inclined member (14). When the inclined member (14) is connected to the rear edge portion (11e), the rear end of the second door impact beam (20b) is connected to the inclined member (14).

Description

Automobile side door and automobile

[0001] The present disclosure relates to a vehicle side door and a vehicle.

[0002] Automobiles are required to have a high level of crashworthiness, and are required to have a structure that can ensure interior space for occupant protection in the event of a collision. The types of collisions that can be expected for automobiles include side collisions, full-overlap frontal collisions, and small-overlap frontal collisions.

[0003] In order to improve the crashworthiness of automobiles, door impact beams are sometimes provided inside side doors (see, for example, Patent Document 1). The door impact beams are typically joined to the door bodies that constitute the side doors.

[0004] Patent Document 1 describes a door structure including a door impact beam. The door structure described in Patent Document 1 is provided with two door impact beams (a first impact bar and a second impact bar). The first impact bar is disposed below the door body, and the second impact bar is disposed near the belt line. A reinforcement is further provided in the belt line. Patent Document 1 describes that the two door impact beams and the reinforcement increase the rigidity of the entire door body, making it possible to prevent deformation of the door body during a side collision.

[0005] Japanese Patent Application Publication No. 10-250369

[0006] For collision safety reasons, automobile side doors 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 reduce the weight of their bodies to improve fuel efficiency. Therefore, side doors must be both lightweight and crashworthy.

[0007] 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.

[0008] An object of the present disclosure is to provide a side door of an automobile and an automobile that can achieve both crashworthiness in a side collision and weight reduction.

[0009] The vehicle side door according to the present disclosure includes a door body, a first door impact beam, a second door impact beam, and a tilting member. The first door impact beam is disposed along the vehicle length direction of the vehicle and is joined to the door body. The second door impact beam is shorter than the first door impact beam. The second door impact beam is disposed lower than the first door impact beam in the vehicle height direction of the vehicle and spaced apart from the first door impact beam, and is joined to the door body. The tilting member is connected to a lower edge of the door body and a front edge or rear edge of the door body. The tilting member is tilted with respect to the vehicle length direction and the vehicle height direction. When the tilting member is connected to the front edge of the door body, a front end of the second door impact beam in the longitudinal direction is connected to the tilting member. When the tilting member is connected to the rear edge of the door body, a rear end of the second door impact beam in the longitudinal direction is connected to the tilting member.

[0010] The automobile according to the present disclosure includes the above-described side door.

[0011] The automobile side door and automobile according to the present disclosure can achieve both crashworthiness against side collisions and lightweight construction.

[0012] FIG. 1 is a schematic diagram showing the overall configuration of an automobile. FIG. 2 is a schematic diagram of a side door according to the first embodiment. FIG. 3 is a perspective view of a door impact beam. FIG. 4 is a perspective view of the door impact beam. FIG. 5 is a cross-sectional view of the beam body. FIG. 6 is a cross-sectional view of the beam body of a side door according to the second embodiment. FIG. 7 is a partially enlarged view of FIG. 6. FIG. 8 is a schematic view of a modified side door. FIG. 9 is a schematic view of a modified side door. FIG. 10 is a schematic view of a modified side door. FIG. 11 is a schematic view of a modified side door. FIG. 12 is a perspective view of a modified door impact beam. FIG. 13 is a perspective view of a modified door impact beam. FIG. 14 is a diagram summarizing the results of the examples. FIG. 15 is a diagram summarizing the results of the examples.

[0013] According to an embodiment, a vehicle side door includes a door body, a first door impact beam, a second door impact beam, and a tilting member. The first door impact beam is disposed along the vehicle length direction of the vehicle and is joined to the door body. The second door impact beam is shorter than the first door impact beam. The second door impact beam is disposed lower than the first door impact beam in the vehicle height direction of the vehicle and spaced apart from the first door impact beam, and is joined to the door body. The tilting member is connected to a lower edge of the door body and a front edge or a rear edge of the door body. The tilting member is tilted with respect to the vehicle length direction and the vehicle height direction. When the tilting member is connected to the front edge of the door body, a front end of the second door impact beam in the longitudinal direction is connected to the tilting member. When the tilting member is connected to the rear edge of the door body, a rear end of the second door impact beam in the longitudinal direction is connected to the tilting member (first configuration).

[0014] The side door of the first configuration has two door impact beams. The second door impact beam is positioned lower than the first door impact beam. When a load is generated on the vehicle due to a side collision, each door impact beam is subjected to a bending moment corresponding to its length. Here, because the second door impact beam is shorter than the first door impact beam, the bending moment generated in the second door impact beam is relatively small. Therefore, the side door of the first configuration can ensure high crashworthiness against side collisions. The improved crashworthiness allows the thickness of each door impact beam and the door body to be reduced, thereby reducing the weight of the side door. As a result, both crashworthiness and weight reduction can be achieved.

[0015] The side door preferably has the following configuration: The door body includes a beltline portion extending in the vehicle length direction. The first door impact beam is disposed at the beltline portion in the vehicle height direction. At least one longitudinal end of the second door impact beam is disposed at a position lower than the midpoint between the lower edge of the door body and the beltline portion in the vehicle height direction (second configuration). Generally, an EV is equipped with a battery in the lower portion of the vehicle body. Therefore, from the viewpoint of battery protection, it is necessary to ensure collision resistance, particularly in the lower portion of the vehicle body. In the side door of the second configuration, at least one end of the second door impact beam is disposed at a position lower than the midpoint of the door body. In other words, the second door impact beam is disposed at a relatively low position. This ensures collision resistance in the lower portion of the vehicle body.

[0016] In the side door of the second configuration, both ends of the second door impact beam in the longitudinal direction may be positioned lower than the mid-height of the door body in the vehicle height direction (third configuration). In the side door of the third configuration, both ends of the second door impact beam are positioned lower than the mid-height of the door body, so the second door impact beam is positioned even lower than in the side door of the second configuration. This ensures crash resistance in the lower part of the vehicle body.

[0017] In the above-described side door, the inclined member may be a member formed separately from the second door impact beam (fourth configuration).

[0018] In the above-described side door, the inclined member may be a member that is molded integrally with the second door impact beam (fifth configuration).

[0019] The side door preferably has the following configuration: the door body includes a belt line portion extending in the vehicle length direction, and the front end portion of the second door impact beam in the longitudinal direction is positioned at a position lower than the midpoint between the lower edge of the door body and the belt line portion in the vehicle height direction (sixth configuration).

[0020] The side door preferably has the following configuration: The door body includes an inner panel and an outer panel joined to the inner panel. The inclined member is joined to a surface of the outer panel facing the inner panel (seventh configuration). By joining the inclined member to the outer panel, the rigidity of the outer panel can be increased.

[0021] The side door preferably has the following configuration: the door main body includes a door hinge portion, and a front end portion in the longitudinal direction of the first door impact beam is joined to the door hinge portion (eighth configuration).

[0022] The side door preferably has the following configuration: the door main body includes a door hinge portion, and when the inclined member is connected to the rear edge portion of the door main body, a front end portion in the longitudinal direction of the second door impact beam is joined to the door hinge portion (ninth configuration).

[0023] In the above-mentioned side door, at least one of the first door impact beam and the second door impact beam may include a first plate portion, a second plate portion, a first end flange portion, and a second end flange portion. The second plate portion extends in the longitudinal direction of the first plate portion 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 connected to an end portion 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. The first end flange portion and the second end flange portion are each joined to the door body (tenth configuration).

[0024] In a tenth configuration, at least one end of the first door impact beam and the second door impact beam includes a first end flange portion and a second end flange 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. This continuous flange portion is joined to the door body constituting the side door, allowing for a surface joint rather than a point joint. Furthermore, because the continuous flange portion that forms the joint surface with the door body is continuous, the area of ​​the joint surface is increased, allowing for the load generated by a frontal collision to be dispersed. Therefore, the door impact beam of the tenth configuration can ensure high crash resistance in frontal collisions.

[0025] The side door may be a front door of a vehicle (eleventh configuration).

[0026] In the above-mentioned side door, at least a portion of the first door impact beam and the second door impact beam may be formed of a plate-shaped surface-softened portion, wherein 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 of the plate thickness direction (twelfth configuration). In the twelfth 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 of 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.

[0027] The side door of the twelfth 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 (thirteenth configuration).

[0028] In the thirteenth configuration, the Vickers hardness of the surface-softened portion at the center in the thickness direction is 400 HV or more, which makes it easy to significantly improve the deformability of the surface-softened portion. Furthermore, the thickness of the softened portion is 20% or less of the thickness of the surface-softened portion, which reduces the ratio of the volume of the softened portion to the total volume of the surface-softened portion, thereby ensuring the load-bearing capacity of the surface-softened portion. Furthermore, the thickness of the softened portion is 80 μm or more and 5% or more of the thickness of the surface-softened portion, which makes it possible to fully demonstrate the deformability of the softened portion.

[0029] In the thirteenth configuration, the Vickers hardness of the surface of the softened surface portion is at least 0.5 times 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 thirteenth configuration, ΔHV1 is greater than ΔHV2, thereby improving the crashworthiness of the softened surface portion.

[0030] An automobile according to an embodiment includes the above-described side door (fourteenth configuration).

[0031] 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.

[0032] [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 a front door 10a and a rear door 10b as side doors. The rear door 10b has substantially the same configuration as the front door 10a. Hereinafter, when there is no need to distinguish between the front door 10a and the rear door 10b, they may be simply referred to as "side doors 10."

[0033] [Side Door] Fig. 2 is a schematic diagram of the side door 10 according to the first embodiment. Fig. 2 shows the side door 10 as viewed from the vehicle interior side. In the example shown in Fig. 2, the side door 10 is a front door 10a. Referring to Fig. 2, the side door 10 includes a door body 11 and a window frame 12 joined to the door body 11. The door body 11 includes an inner panel 111 and an outer panel 112 (Fig. 1). The outer panel 112 is joined to the outside of the inner panel 111.

[0034] The door body 11 includes a beltline portion 11a extending in the vehicle length direction of the automobile 1. The beltline portion 11a corresponds to the lower edge of the window frame 12. The side door 10 includes two door impact beams, namely, a first door impact beam 20a and a second door impact beam 20b, as reinforcing members for enhancing collision resistance. The first door impact beam 20a is disposed along the vehicle length direction. The second door impact beam 20b is disposed at a lower position than the first door impact beam 20a in the vehicle height direction of the automobile 1 and spaced apart from the first door impact beam 20a. In this embodiment, the second door impact beam 20b is disposed at an angle with respect to the vehicle length direction. Hereinafter, when there is no need to distinguish between the first door impact beam 20a and the second door impact beam 20b, they may be simply referred to as "door impact beams 20."

[0035] The door main body 11 includes a door hinge portion 11b. The door hinge portion 11b serves as a fulcrum when the side door 10 is opened or closed. The side door 10 is attached to the body of the automobile 1 via the door hinge portion 11b. The door hinge portion 11b is fixed to the door main body 11 while passing through a front edge portion 11c of the door main body 11 in the vehicle length direction. In the example shown in FIG. 2, two door hinge portions 11b are arranged spaced apart in the vehicle height direction.

[0036] The side door 10 further includes a tilting member 14. In this embodiment, the tilting member 14 is a member molded separately from the second door impact beam 20b. The tilting member 14 is joined to the lower edge 11d of the door body 11 and the front edge 11c or rear edge 11e of the door body 11. In the example shown in FIG. 2, the tilting member 14 is joined to the lower edge 11d of the door body 11 and the rear edge 11e of the door body 11. The tilting member 14 is tilted in both the vehicle length direction and the vehicle height direction. At least a portion of the tilting member 14 is joined to the surface of the outer panel 112 facing the inner panel 111, i.e., the inner surface. The tilting member 14 and the outer panel 112 are joined together with, for example, a mastic adhesive. By joining the tilting member 14 to the outer panel 112, the rigidity of the outer panel 112 can be increased.

[0037] The positions of the first door impact beam 20a and the second door impact beam 20b are not particularly limited. In the example shown in Fig. 2, the first door impact beam 20a is disposed below the belt line portion 11a. However, the first door impact beam 20a may be disposed at the position of the belt line portion 11a in the vehicle height direction. The first door impact beam 20a disposed at the position of the belt line portion 11a may be called a belt line reinforcement.

[0038] 2, one longitudinal end of the second door impact beam 20b is located at a position lower than the midpoint H between the lower edge 11d of the door body 11 and the belt line 11a in the vehicle height direction. Specifically, the front end of the second door impact beam 20b is located at a position higher than the midpoint H, and the rear end of the second door impact beam 20b is located at a position lower than the midpoint H.

[0039] When only one longitudinal end of the second door impact beam 20b is lower than the mid-height H, it does not matter which end is lower, but it is preferable that the rear end of the second door impact beam 20b is lower than the mid-height H. This is because when a load is generated on the automobile 1 due to a frontal collision, the load transmitted to the rear edge 11e of the door body 11 is dispersed, thereby reducing the load burden on the rear edge 11e.

[0040] The first door impact beam 20a and the second door impact beam 20b are each joined to the door body 11. The front end of the first door impact beam 20a in the longitudinal direction is joined to the door hinge portion 11b, and the rear end is joined to the rear edge portion 11e of the door body 11 (inner panel 111). Because the front end of the first door impact beam 20a is joined to the door hinge portion 11b, the first door impact beam 20a is not directly joined to the inner panel 111. In this case, the transmission of load from the first door impact beam 20a to the inner panel 111 is suppressed, and the load burden on the inner panel 111 can be reduced.

[0041] The front or rear end of the second door impact beam 20b in the longitudinal direction is connected to the inclined member 14. Specifically, when the inclined member 14 is connected to the front edge 11c of the door body 11, the front end of the second door impact beam 20b in the longitudinal direction is connected to the inclined member 14. When the inclined member 14 is connected to the rear edge 11e of the door body 11, the rear end of the second door impact beam 20b in the longitudinal direction is connected to the inclined member 14. In the example shown in FIG. 2, the inclined member 14 is connected to the rear edge 11e of the door body 11, so that the front end of the second door impact beam 20b in the longitudinal direction is joined to the front edge 11c of the door body 11 (inner panel 111), and the rear end is connected to the inclined member 14. Therefore, the second door impact beam 20b is shorter than the first door impact beam 20a. When the inclined member 14 is connected to the rear edge portion 11e of the door body 11, the front end of the second door impact beam 20b may be joined to the door hinge portion 11b instead of the front edge portion 11c of the door body 11.

[0042] 3 and 4 are perspective views of the door impact beam 20. Fig. 3 shows the front end of the door impact beam 20 in the longitudinal direction, and Fig. 4 shows the rear end of the door impact beam 20 in the longitudinal direction. With reference to Figs. 3 and 4, in this embodiment, the door impact beam 20 includes a beam body 30 and continuous flange portions 40 and 50. The beam body 30 extends in the longitudinal direction of the door impact beam 20. The continuous flange portion 40 is connected to the front end of the beam body 30, and the continuous flange portion 50 is connected to the rear end of the beam body 30.

[0043] The door impact beam 20 is joined to the door body 11 ( FIG. 2 ) and / or the inclined member 14 via continuous flange portions 40, 50 provided at both ends. In other words, the continuous flange portions 40, 50 serve as the joining surface with the door body 11. The method for joining the door impact beam 20 to the door body 11 and the inclined member 14 is not particularly limited, but may be, for example, welding. Arc welding or laser welding may be used as the welding method. The shape of the continuous flange portions 40, 50 is not particularly limited. For example, the continuous flange portions 40, 50 have a shape corresponding to the mounting portion of the door body 11 (or the inclined member 14) to which they are joined.

[0044] FIG. 5 is a cross-sectional view of the beam body 30. The cross-sectional view refers to a cross-section taken perpendicular to the longitudinal direction of the door impact beam 20. Referring to FIGS. 3 to 5, the beam body 30 includes a first plate portion 31, a second plate portion 32, a third plate portion 33, a first side flange portion 34, and a second side flange portion 35. The first plate portion 31, the second plate portion 32, the third plate portion 33, the first side flange portion 34, and the second side flange portion 35 are each flat and extend in the longitudinal direction of the door impact beam 20. In this embodiment, the beam body 30 has a hat-shaped cross-section. However, the cross-sectional shape of the beam body 30 is not limited to this and may be L-shaped or U-shaped.

[0045] In this embodiment, the first plate portion 31 corresponds to the top plate of the hat-shaped beam body 30, and the second plate portion 32 and the third plate portion 33 correspond to the vertical walls of the beam body 30. Hereinafter, the width direction of the first plate portion 31 may be referred to as the width direction of the door impact beam 20, and the direction perpendicular to the first plate portion 31 may be referred to as the height direction of the door impact beam 20. Note that the height direction of the door impact beam 20 may differ from the vehicle height direction of the automobile 1.

[0046] The second plate portion 32 is connected to one side of the first plate portion 31 via a ridge portion 321. The third plate portion 33 is connected to the other side of the first plate portion 31 via a ridge portion 331. The ridge portions 321 and 331 each have a substantially arc shape when viewed in cross section of the beam body 30.

[0047] The first side flange portion 34 is connected to a side portion of the second plate portion 32 opposite to the first plate portion 31 via a ridge portion 322. The first side flange portion 34 protrudes from the second plate portion 32 on the side opposite to the first plate portion 31 in the width direction. The second side flange portion 35 is connected to a side portion of the third plate portion 33 opposite to the first plate portion 31 via a ridge portion 332. The second side flange portion 35 protrudes from the third plate portion 33 on the side opposite to the first plate portion 31 in the width direction. The ridge portions 322 and 332 each have a substantially arc shape in a cross-sectional view of the beam body 30.

[0048] 3, the continuous flange portion 40 has an L-shape when viewed from the side of the door impact beam 20. 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 second end flange portion 42 and the third end flange portion 43 are each continuous with the first end flange portion 41.

[0049] The first end flange portion 41 is connected to the front end portion in the longitudinal direction of the first plate portion 31. The first end flange portion 41 protrudes forward in the longitudinal direction from the first plate portion 31. The width of the first end flange portion 41 is the same as the width of the entire beam body 30. Therefore, the width of the first end flange portion 41 is greater than the width of the first plate portion 31.

[0050] The second end flange 42 is connected to the longitudinal front end of the second plate 32 via a ridge 421. The second end flange 42 protrudes from the second plate 32 in the width direction toward the opposite side to the first plate 31. The second end flange 42 is disposed at a right angle to the second plate 32. However, the angle of the second end flange 42 relative to the second plate 32 does not have to be a right angle.

[0051] The third end flange 43 is connected to the longitudinal front end of the third plate 33 via a ridge 431. The third end flange 43 protrudes from the third plate 33 on the opposite side to the first plate 31 in the width direction. The third end flange 43 is disposed at a right angle to the third plate 33. However, the angle of the third end flange 43 relative to the third plate 33 does not have to be a right angle.

[0052] The second end flange portion 42 and the third end flange portion 43 each intersect with the longitudinal direction. The second end flange portion 42 is connected to the first side flange portion 34 via a ridge portion 422, and the third end flange portion 43 is connected to the second side flange portion 35 via a ridge portion 432. The angle between the second end flange portion 42 and the first end flange portion 41 and the angle between the third end flange portion 43 and the first end flange portion 41 are, for example, 90° or more and 135° or less. These angles may also be 120° or less.

[0053] 4 , the continuous flange portion 50 is flat. The continuous flange portion 50 intersects the longitudinal direction. The continuous flange portion 50 includes a first end flange portion 51, a second end flange portion 52, and a third end flange portion 53. The second end flange portion 52 and the third end flange portion 53 are each continuous with the first end flange portion 51.

[0054] The first end flange 51 is connected to the longitudinal rear end of the first plate 31 via a ridge 511. The first end flange 51 protrudes from the first plate 31 on the opposite side to the second plate 32 and the third plate 33 in the height direction.

[0055] The second end flange portion 52 is connected to the rear end portion in the longitudinal direction of the second plate portion 32 via a ridge portion 521. The second end flange portion 52 protrudes from the second plate portion 32 on the side opposite to the first plate portion 31 in the width direction. The second end flange portion 52 is disposed at a right angle to the second plate portion 32. However, the angle of the second end flange portion 52 relative to the second plate portion 32 does not have to be a right angle.

[0056] The third end flange portion 53 is connected to the longitudinal rear end of the third plate portion 33 via a ridge portion 531. The third end flange portion 53 protrudes from the third plate portion 33 on the opposite side to the first plate portion 31 in the width direction. The third end flange portion 53 is disposed at a right angle to the third plate portion 33. However, the angle of the third end flange portion 53 relative to the third plate portion 33 does not have to be a right angle.

[0057] The second end flange portion 52 and the third end flange portion 53 are each located on the same plane as the first end flange portion 51. The second end flange portion 52 is connected to the first side flange portion 34 via a ridge portion 522, and the third end flange portion 53 is connected to the second side flange portion 35 via a ridge portion 532.

[0058] At least a portion of the first door impact beam 20a and the second door impact beam 20b may be composed of a plate-shaped surface-softened portion 60. An example in which the entire beam body 30 of the first door impact beam 20a and the second door impact beam 20b is composed of the surface-softened portion 60 will be described below. However, the continuous flange portions 40, 50 may also be composed of the surface-softened portion 60. Alternatively, only a portion of the beam body 30 and / or the continuous flange portions 40, 50 may be composed of the surface-softened portion 60. The surface-softened portion 60 is preferably provided in a portion of the beam body 30 and / or the continuous flange portions 40, 50 that is particularly prone to cracking. The surface-softened portion 60 is preferably provided in the longitudinal center of the beam body 30. In this case, the crash resistance of the door impact beam 20 can be improved, particularly in side collisions.

[0059] As described above, with reference to FIG. 5 , the beam body 30 is formed from the surface-softened portion 60. The Vickers hardness of the surface 60 a of the surface-softened portion 60 is lower than the Vickers hardness at the center of the surface-softened portion 60 in the thickness direction. The Vickers hardness of the surface 60 a of the surface-softened portion 60 is, for example, 100 HV or more lower than the Vickers hardness at the center of the surface-softened portion 60 in the thickness direction. This improves the bending deformability of the surface-softened portion 60 (beam body 30), making it easier for the surface-softened portion 60 to absorb impacts. Examples of upper limits for the difference between the Vickers hardness of the surface 60 a of the surface-softened portion 60 and the Vickers hardness at the center of the surface-softened portion 60 in the thickness direction include 250 HV, 300 HV, 350 HV, 400 HV, 500 HV, 550 HV, 600 HV, and 650 HV.

[0060] If the Vickers hardness of the surface 60a of the surface-softened portion 60 is 0.5 times or more the Vickers hardness at the center of the surface-softened portion 60 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 60a of the surface-softened portion 60 is 0.6 times or more the Vickers hardness at the center of the surface-softened portion 60 in the plate thickness direction. On the other hand, if the Vickers hardness of the surface 60a of the surface-softened portion 60 is less than 0.9 times the Vickers hardness at the center of the surface-softened portion 60 in the plate thickness direction, the deformability of the surface-softened portion 60 can be sufficiently improved. More preferably, the Vickers hardness of the surface 60a of the surface-softened portion 60 is less than 0.8 times the Vickers hardness at the center of the surface-softened portion 60 in the plate thickness direction.

[0061] The Vickers hardness of the surface-softened portion 60 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 60 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 60.

[0062] The Vickers hardness of the surface 60a of the surface-softened portion 60 is measured on a cross section obtained by cutting the surface-softened portion 60 along the plate thickness direction in accordance with the Vickers hardness test described in JIS Z 2244:2020.

[0063] 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.

[0064] 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 60 a of the surface-softened portion 60. If a plating layer is present in the surface-softened portion 60, 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 60, 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 60 a of the surface-softened portion 60.

[0065] [Effects] The side door 10 according to this embodiment includes a first door impact beam 20a and a second door impact beam 20b. When a load is generated on the vehicle 1 due to a side collision, a bending moment acts on each door impact beam 20a, 20b according to its length. The second door impact beam 20b is shorter than the first door impact beam 20a. Therefore, the bending moment generated in the second door impact beam 20b is relatively small. Therefore, the side door 10 according to this embodiment can ensure high crashworthiness against side collisions. The improved crashworthiness allows the thickness of each door impact beam 20a, 20b and the door body 11 to be reduced, thereby reducing the weight of the side door 10. As a result, both crashworthiness and weight reduction can be achieved.

[0066] In the side door 10 according to this embodiment, one longitudinal end of the second door impact beam 20b is positioned at a position lower than the mid-height H of the door body 11. In other words, the second door impact beam 20b is positioned at a relatively low position. This ensures collision resistance in the lower part of the vehicle body. The first door impact beam 20a of the side door 10 according to this embodiment may be positioned at the belt line portion 11a. In this case, even if the second door impact beam 20b is positioned at a relatively low position, collision resistance in the upper part of the vehicle body can also be ensured.

[0067] [Second embodiment] Fig. 6 is a cross-sectional view of the beam body 30 of a side door according to a second embodiment. In this embodiment, as shown in Fig. 6, the surface softened portion 60 is formed of a hardened portion 61 and a softened portion 62.

[0068] The hardened portion 61 includes the central portion of the surface-softened portion 60 (beam body 30) in the plate thickness direction. The softened portion 62 is laminated on the hardened portion 61. The softened portion 62 is provided, for example, on both sides of the hardened portion 61 in the plate thickness direction. The softened portions 62 are respectively arranged along the surface 60a on both sides of the surface-softened portion 60 in the plate thickness direction. In this case, the hardened portion 61 is arranged between the softened portions 62. However, the softened portion 62 may be provided on only one side of the hardened portion 61 in the plate thickness direction.

[0069] The thickness of the softened portion 62 is preferably 80 μm or more from the viewpoint of ensuring sufficient strength of the surface-softened portion 60. The thickness of the softened portion 62 may be 200 μm or less. Furthermore, the thickness of the softened portion 62 may be 5% or more and 20% or less of the plate thickness of the surface-softened portion 60. If the thickness of the softened portion 62 is 20% or less of the plate thickness of the surface-softened portion 60, the ratio of the volume of the softened portion 62 to the volume of the surface-softened portion 60 is small, and therefore the load-bearing capacity of the surface-softened portion 60 can be ensured. The thickness of the softened portion 62 is preferably 17% or less of the thickness of the surface-softened portion 60, and more preferably 14% or less. On the other hand, when the softened portion 62 is provided over the entire surface 60a of the surface-softened portion 60, the deformability of the softened portion 62 can be fully exhibited if the thickness of the softened portion 62 is 80 μm or more and 5% or more of the plate thickness of the surface-softened portion 60. It is more preferable that the thickness of the softened portion 62 is 8% or more of the plate thickness of the surface-softened portion 60.

[0070] The hardened portion 61 has a constant Vickers hardness in the plate thickness direction. The Vickers hardness of the hardened portion 61 is preferably 400 HV or higher. When the Vickers hardness of the hardened portion 61 is 400 HV or higher, the deformability of the surface-softened portion 60 is likely to be significantly improved. The Vickers hardness of the hardened portion 61 is more preferably 500 HV or higher, and even more preferably 600 HV or higher. The Vickers hardness of the hardened portion 61 may be 700 HV or higher. There is no particular upper limit to the Vickers hardness of the hardened portion 61, 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 61 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 61 include 1100 HV, 1050 HV, 1000 HV, 950 HV, 900 HV, 850 HV, and 800 HV. The Vickers hardness of the hardened portion 61 may be 350 HV or more and 770 HV or less.

[0071] The Vickers hardness of the softened portion 62 varies in the thickness direction. Specifically, the Vickers hardness of the softened portion 62 gradually decreases from the center side in the thickness direction of the surface-softened portion 60 toward the surface 60a side. In other words, the Vickers hardness of the softened portion 62 is smallest at the surface 60a of the surface-softened portion 60.

[0072] The position of the boundary between the softened portion 62 and the hardened portion 61 can be measured as follows. A cross section perpendicular to the plate surface of the sample cut from the surface-softened portion 60 is taken, and the sample surface to be measured is prepared and submitted to 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 on the measurement surface using a sample rotating holder manufactured by JEOL Ltd.

[0073] The Vickers hardness of the sample with the prepared measurement surface is measured using a micro Vickers hardness tester. The hardness is measured in a region from the surface of the sample corresponding to the softened portion 62 of the sample in a direction perpendicular to the surface (thickness direction) with a test force of 50 gf.

[0074] 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 60a of the surface-softened portion 60. If a plating layer is present in the surface-softened portion 60, 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 60, 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.

[0075] 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 60a of the surface-softened portion 60; xk: thickness position (μm) from the surface 60a of the surface-softened portion 60; yk: average value (HV) of Vickers hardness at three different points at the thickness position xk.

[0076] Of the three measurement points at which the slope Δbi calculated by equation (1) from the surface 60a side of the surface softened portion 60 first becomes 0.5 (HV / μm) or less, the thickness position of the measurement point closest to the surface 60a is determined to be the boundary position between the softened portion 62 and the hardened portion 61.

[0077] Fig. 7 is a partially enlarged view of Fig. 6. As shown in Fig. 7, the softened portion 62 preferably includes a first region A1 and a second region A2. The first region A1 is a region from the surface 60a of the surface-softened portion 60 to 40% of the thickness of the softened portion 62. The second region A2 is a region of the softened portion 62 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 62.

[0078] 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 62 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 60 a of the surface-softened portion 60 (a thickness range of 48 μm). When the thickness of the softened portion 62 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 60 a of the surface-softened portion 60 (a thickness range of 120 μm).

[0079] 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 60 is improved. The method of calculating ΔHV1 and ΔHV2 will be described later.

[0080] 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 60 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 60 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 60 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.

[0081] 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 60 is taken, and the sample surface is prepared for hardness testing. The measurement surface is prepared 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.

[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 62 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.

[0083] The measurement position on the surface-most side of the sample is 20 μm thick from the surface 60 a of the surface-softened portion 60. If a plating layer is present in the surface-softened portion 60, 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 60, 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 60 a of the surface-softened portion 60 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, 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.

[0084] The Vickers hardness of the second region A2 is measured within the softened portion 62, 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 62 and the hardened portion 61, and two points between these two points. When the second region A2 is present up to a position 200 μm from the surface 60 a, the measurement points of 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 60 a.

[0085] When the softened portion 62 is provided on both sides of the hardened portion 61 in the thickness direction, the same measurement is also performed on the opposite surface 60a of the sample.

[0086] 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 60 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 62; 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.

[0087] When the softened portion 62 is provided on both sides of the hardened portion 61 in the plate thickness direction, the gradient Δa1 on one surface 60a side is calculated from equation (2), and then the gradient Δa2 on the other surface 60a side is calculated from equation (2). The arithmetic mean of Δa1 and Δa2 can be set to Δa.

[0088] 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 62.

[0089] 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 60 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 62; 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.

[0090] When the softened portion 62 is provided on both sides of the hardened portion 61 in the plate thickness direction, the gradient ΔA1 on one surface 60a side is calculated from equation (3), and then the gradient ΔA2 on the other surface 60a side is calculated from equation (3). The arithmetic mean of ΔA1 and ΔA2 can then be taken as ΔA.

[0091] 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 62.

[0092] There are no particular limitations on the method for forming the softened portion 62 in the surface-softened portion 60. The softened portion 62 is formed, for example, by reducing the carbon content of a portion of the blank that is the material for the surface-softened portion 60 that will become the softened portion 62 (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 61.

[0093] 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.

[0094] In the above embodiment, one longitudinal end of the second door impact beam 20b is located lower than the midpoint H between the lower edge 11d of the door body 11 and the beltline 11a, and the other longitudinal end of the second door impact beam 20b is located higher than the midpoint H. However, both longitudinal ends of the second door impact beam 20b may be located higher than the midpoint H, or both longitudinal ends may be located lower than the midpoint H. FIG. 8 is a diagram showing a modified example of the side door 10. In the example shown in FIG. 8, both longitudinal ends of the second door impact beam 20b are located lower than the midpoint H. In this case, the second door impact beam 20b is located lower than the side door 10 shown in FIG. 2. This ensures collision resistance at the lower part of the vehicle body. In the example shown in FIG. 8, the front longitudinal end of the second door impact beam 20b is joined to the door hinge 11b, and the rear longitudinal end is joined to the inclined member 14.

[0095] In the above embodiment, the inclined member 14 is a member molded separately from the second door impact beam 20b. However, the inclined member 14 may be a member molded integrally with the second door impact beam 20b. FIGS. 9 and 10 are schematic diagrams of modified side door 10. In the example shown in FIG. 9, the second door impact beam 20b of the side door 10 shown in FIG. 2 is integrated with the inclined member 14. In this case, the member consisting of the second door impact beam 20b and the inclined member 14 has a T-shape in a side view of the automobile 1. In the example shown in FIG. 10, the second door impact beam 20b is connected to two inclined members 14a, 14b by a connecting portion 141. The inclined member 14a is joined to the lower edge 11d of the door body 11, and the inclined member 14b is joined to the rear edge 11e of the door body 11. In this case, the member consisting of the second door impact beam 20b and the inclined members 14a, 14b has a Y-shape in a side view of the automobile 1.

[0096] In the above embodiment, when viewing the side door 10 from the vehicle interior, one of the longitudinal ends of the second door impact beam 20b is close to the edge of the door body 11, while the other end is spaced far away from the edge of the door body 11. For example, in the example shown in FIG. 2 , the front end of the second door impact beam 20b is joined to the front edge 11c of the door body 11 (inner panel 111), and the rear end is spaced apart from the lower edge 11d and rear edge 11e of the door body 11. It can also be said that the distance between the rear end and the edge of the door body 11 (first distance) is greater than the distance between the front end and the edge of the door body 11 (second distance). The first distance is preferably 10% to 30% of the total length (longitudinal dimension) of the second door impact beam 20b. In the above embodiment, the rear end is supported by the inclined member 14, but it may be supported by other methods. For example, the rear end of the second door impact beam 20b may be supported by a support member provided in the inner region of the edge of the door body 11. In this case, the support member may be joined to, for example, the outer panel 112 or to another member.

[0097] In the above embodiment, the inclined member 14 is joined to the lower edge 11d and the rear edge 11e of the door body 11. However, the inclined member 14 may be joined to the lower edge 11d and the front edge 11c of the door body 11 as shown in Fig. 11. In this case, the front end of the second door impact beam 20b in the longitudinal direction is connected to the inclined member 14, and the rear end is joined to the rear edge 11e of the door body 11 (inner panel 111).

[0098] In the above embodiment, the second end flange portions 42, 52 and the third end flange portions 43, 53 of the door impact beam 20, which are joined to the door body 11, are substantially parallel to the width direction. However, as shown in Figures 12 and 13, the second end flange portions 42, 52 and the third end flange portions 43, 53 may be inclined with respect to the width direction.

[0099] To confirm the effects of the present disclosure, an analysis was performed on the side door 10 according to the above embodiment using commercially available structural analysis software (LS-DYNA, manufactured by Livermore Software Technology Corporation). Specifically, an analytical model of the side door 10 was created, and an impactor was inserted into the side of the side door 10. The load (reaction force) generated on the impactor and the stroke (displacement) of the impactor were then investigated.

[0100] In this example, two analytical models were created, Examples 1 and 2. In Example 1, an analytical model of the side door 10 shown in Fig. 2 was created, and in Example 2, an analytical model of the side door 10 shown in Fig. 8 was created. In both Examples 1 and 2, the door impact beams 20a, 20b were each provided with continuous flange portions 40, 50 at both ends. In Examples 1 and 2, the plate thickness of each door impact beam 20a, 20b was 1.4 mm, and the tensile strength was 2.0 GPa.

[0101] As a comparative example, an analytical model was also created for a side door having a different configuration from the side door 10 described above, and analysis was performed in the same manner as in Examples 1 and 2. The side door of the comparative example did not have an inclined member, and the length of the second door impact beam was equal to the length of the first door impact beam. Furthermore, each door impact beam of the comparative example did not have a continuous flange portion at any end. That is, in each door impact beam of the comparative example, the first end flange portion, second end flange portion, and third end flange portion were not continuous but separated from each other. In the comparative example, the tensile strength of each door impact beam was 1.5 GPa. The other conditions of the comparative example were the same as those of Example 1.

[0102] 14 and 15 are graphs summarizing the results of this example. In FIG. 14, the vertical axis represents load, and the horizontal axis represents stroke. In FIG. 15, the vertical axis represents load per unit weight, and the horizontal axis represents stroke. The area of ​​the graphs in FIGS. 14 and 15 represents the absorbed energy of the side door. The results shown in FIG. 14 indicate that the absorbed energy of the side door in Examples 1 and 2 was significantly improved compared to the comparative example. Furthermore, the results shown in FIG. 15 indicate that the absorbed energy per unit weight of the side door in Examples 1 and 2 was also significantly improved compared to the comparative example. This indicates that the side door 10 according to the above embodiment can absorb a side collision load efficiently, thereby suppressing deformation toward the interior of the vehicle. Therefore, it can be seen that this side door 10 has excellent crashworthiness in a side collision.

[0103] 1: Automobile 10: Side door 10a: Front door 10b: Rear door 11: Door body 11a: Belt line portion 11b: Door hinge portion 11c: Front edge portion 11d: Lower edge portion 11e: Rear edge portion 111: Inner panel 112: Outer panel 14: Inclined member 20, 20a, 20b: Door impact beam 31: First plate portion 32: Second plate portion 321: Ridge line portion 41, 51: First end flange portion 42, 52: Second end flange portion 60: Surface softened portion 60a: Surface 61: Hardened portion 62: Softened portion A1: First region A2: Second region

Claims

1. A side door of a motor vehicle, comprising: a door body; a first door impact beam disposed along the vehicle length direction of the motor vehicle and joined to the door body; a second door impact beam shorter than the first door impact beam, disposed at a position lower than the first door impact beam in the vehicle height direction of the motor vehicle with a gap from the first door impact beam, and joined to the door body; and an inclined member connected to a lower edge portion of the door body and a front edge portion or a rear edge portion of the door body, and inclined with respect to the vehicle length direction and the vehicle height direction. When the inclined member is connected to the front edge portion of the door body, a front end portion of the second door impact beam in the longitudinal direction is connected to the inclined member. When the inclined member is connected to the rear edge portion of the door body, a rear end portion of the second door impact beam in the longitudinal direction is connected to the inclined member.

2. The side door according to claim 1, wherein the door body includes a belt line portion extending in the vehicle length direction, the first door impact beam is disposed at a position of the belt line portion in the vehicle height direction, and at least one end portion of the second door impact beam in the longitudinal direction is disposed at a position lower than an intermediate height between the lower edge portion of the door body and the belt line portion in the vehicle height direction.

3. The side door according to claim 2, wherein both end portions of the second door impact beam in the longitudinal direction are disposed at positions lower than the intermediate height of the door body in the vehicle height direction, respectively.

4. The side door according to claim 1, wherein the inclined member is a member formed separately from the second door impact beam.

5. The side door according to claim 1, wherein the inclined member is a member formed integrally with the second door impact beam.

6. The side door according to claim 1, wherein the door body includes a belt line portion extending in the vehicle length direction, and a front end portion of the second door impact beam in the longitudinal direction is disposed at a position lower than an intermediate height between a lower edge portion and the belt line portion of the door body in the vehicle height direction.

7. The side door according to claim 1, wherein the door body includes an inner panel and an outer panel joined to the inner panel, and the inclined member is joined to a surface of the outer panel on the inner panel side.

8. The side door according to claim 1, wherein the door body includes a door hinge portion, and a front end portion of the first door impact beam in the longitudinal direction is joined to the door hinge portion.

9. The side door according to claim 1, wherein the door body includes a door hinge portion, and when the inclined member is connected to a rear edge portion of the door body, a front end portion of the second door impact beam in the longitudinal direction is joined to the door hinge portion.

10. The side door according to claim 1, wherein at least one of the first door impact beam and the second door impact beam includes a first plate portion, a second plate portion extending in the longitudinal direction of the first plate portion 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, and the first end flange portion and the second end flange portion are each joined to the door body.

11. The side door according to claim 1, which is a front door of the automobile.

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

13. The side door according to claim 12, wherein the surface softening portion is formed of a hardened portion and a softening portion laminated on the hardened 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 that is a region from the surface of the surface softening portion to 40% of the thickness of the softening portion, and a second region that 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.

14. An automobile comprising the side door according to any one of claims 1 to 13.

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