Side member and vehicle body

Abstract

A side member (10) for a vehicle body (1) comprises an upper plate (11), a lower plate (12), and a side plate (13). The lower plate (12) is disposed below the upper plate (11) in a state in which the side member (10) is attached to the vehicle body (1). The side plate (13) connects the upper plate (11) with the lower plate (12) on one side in the left-right direction of the vehicle body (1) such that, in a state in which the side member (10) is attached to the vehicle body (1), there is an opening between the upper plate (11) and the lower plate (12) on another side in the left-right direction. In a cross-sectional view of the side member (10), when the length of the upper plate (11) is W1, the length of the lower plate (12) is W2, and the length of the side plate (13) is H, a cross-sectional index I represented by I = (W1 + W2) / H is greater than 2.50.

Description

Side members and body

[0001] The present disclosure relates to a side member for a vehicle body and a vehicle body.

[0002] Side members are a type of structural component used in the body of an automobile or other vehicle. They are located on the sides of the vehicle body and extend in the longitudinal direction. When a vehicle or other vehicle experiences a frontal collision, the side members deform and absorb the impact. Therefore, side members are required to have high load-bearing capacity (energy absorption capacity).

[0003] The side member has, for example, a closed cross section. In this case, the side member has cross-sectional strength and can absorb energy by maintaining the closed cross section while undergoing crushing or bending deformation when subjected to a collision load. Side members with closed cross sections are manufactured, for example, by press-forming steel plates into a predetermined shape and then joining the press-formed parts together by spot welding.

[0004] For example, Patent Document 1 discloses a front side member having a closed cross section. The front side member in Patent Document 1 includes an inner panel having a hat-shaped cross section and an outer panel. The inner panel and the outer panel are joined by welding to form the closed cross section.

[0005] JP 2014-128998 A

[0006] In recent years, there has been a demand for reducing greenhouse gas emissions in the automotive industry. One method of reducing greenhouse gas emissions is to reduce the weight of the vehicle body. For example, the weight of the vehicle body can be reduced by thinning the structural members used in the body. However, simply thinning the structural members reduces the crashworthiness of the structural members.

[0007] One possible way to compensate for the decline in crashworthiness is to increase the strength of the materials constituting the structural members. To achieve further weight reduction while maintaining crashworthiness, high-strength materials, such as high-strength steel plates with a tensile strength of 980 MPa, can be used for the structural members. However, it is generally known that high-strength materials have low ductility and weld strength. Therefore, if high-strength materials are used for side members with a closed cross-section structure as described in Patent Document 1, there is a risk of weld fracture in addition to material fracture when the side member is subjected to a collision load. If weld fracture occurs, the side member will no longer be able to maintain its closed cross-section, and the reaction force during a collision will be significantly reduced. Therefore, it is difficult to reduce the weight of structural members while maintaining crashworthiness.

[0008] An object of the present disclosure is to provide a side member for a vehicle body that can be made lighter while ensuring collision resistance.

[0009] A vehicle body side member according to the present disclosure includes an upper plate, a lower plate, and a side plate. The lower plate is disposed below the upper plate when the side member is attached to the vehicle body. The side plate connects the upper plate and the lower plate on one side of the vehicle body in the left-right direction so that an opening is formed between the upper plate and the lower plate on the other side of the vehicle body in the left-right direction when the side member is attached to the vehicle body. When viewed in cross section of the side member, the length of the upper plate is W1, the length of the lower plate is W2, and the length of the side plate is H, and the cross-sectional index I, expressed as I = (W1 + W2) / H, is greater than 2.50.

[0010] According to the vehicle body side member according to the present disclosure, it is possible to reduce the weight while ensuring collision resistance.

[0011] FIG. 1 is a perspective view schematically showing a vehicle body equipped with a side member according to the first embodiment. FIG. 2 is a cross-sectional view of the side member according to the first embodiment. FIG. 3 is a cross-sectional view of the side member according to the second embodiment. FIG. 4 is a cross-sectional view of a side member according to a modified example of the second embodiment. FIG. 5 is a cross-sectional view of a side member according to a modified example of the second embodiment. FIG. 6 is a diagram showing an analytical model of a side member serving as a control example. FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 6. FIG. 8 is a diagram showing an example of analytical models of side members according to Examples 1 to 8 and Comparative Examples 2 to 4. FIG. 9 is a diagram showing the analysis results of the Examples. FIG. 10 is a diagram showing the analysis results of the Examples.

[0012] A vehicle body side member according to an embodiment includes an upper plate, a lower plate, and a side plate. The lower plate is disposed below the upper plate when the side member is attached to the vehicle body. The side plate connects the upper plate and the lower plate on one side of the vehicle body in the left-right direction so that an opening is formed between the upper plate and the lower plate on the other side of the vehicle body in the left-right direction when the side member is attached to the vehicle body. When viewed in cross section of the side member, the length of the upper plate is W1, the length of the lower plate is W2, and the length of the side plate is H, and the cross-sectional index I, expressed as I = (W1 + W2) / H, is greater than 2.50 (first configuration).

[0013] Conventional side members have a closed cross-section structure, for example, in which two components are welded together. In such side members, fracture of the welded joints is likely to occur, especially when high-strength materials are used. However, if the side member is simply designed with an open cross-section structure to eliminate the welded joints, the cross-section of the side member will open early when subjected to a collision load, making it prone to fracture deformation. Therefore, side members with an open cross-section structure generally experience lower reaction forces during a collision than side members with a closed cross-section structure.

[0014] In contrast, the side member according to the first configuration can ensure crashworthiness despite having an open cross-sectional structure. Specifically, the cross-sectional index I of the side member according to the first configuration is greater than 2.50. The cross-sectional index I is an index representing the length of the upper panel and the lower panel relative to the length of the side panel. The larger the cross-sectional index I, the greater the cross-sectional line length in the left-right direction of the vehicle body. In other words, by increasing the cross-sectional index I of the side member, the second moment of area in the left-right direction of the vehicle body can be increased. Because the side member according to the first configuration has a cross-sectional index I greater than 2.50, when a load is input along the fore-aft direction of the vehicle body during a collision, lateral bending deformation is unlikely to occur and the reaction force is unlikely to decrease. This improves energy absorption, thereby ensuring crashworthiness.

[0015] The side member according to the first configuration does not require a separate member to close the opening, and therefore can be made lighter than a side member with a closed cross-section structure. Furthermore, the side member according to the first configuration does not have a welded portion for joining to another member. In this case, naturally, the welded portion will not break during a collision. This allows the material of the side member to be made stronger. Therefore, the side member according to the first configuration can be made lighter while maintaining crashworthiness.

[0016] A vehicle body side member according to another embodiment includes an upper plate, a lower plate, a side plate, and a flange. The lower plate is disposed below the upper plate when the side member is attached to the vehicle body. The side plate connects the upper plate and the lower plate on one side of the vehicle body in the left-right direction so that an opening is formed between the upper plate and the lower plate on the other side of the vehicle body in the left-right direction when the side member is attached to the vehicle body. The flange is connected to at least one of the upper plate and the lower plate on the side opposite the side plate. The flange protrudes upward or downward. In a cross-sectional view of the side member, when the length of the upper plate is W1, the length of the lower plate is W2, and the length of the side plate is H, the cross-sectional index I, expressed as I = (W1 + W2) / H, is greater than 0.20 (second configuration).

[0017] Like the side member according to the first configuration, the side member according to the second configuration also ensures crashworthiness despite having an open cross-section structure. Specifically, the section index I of the side member according to the second configuration is greater than 0.20. Therefore, a certain degree of moment of inertia in the lateral direction of the vehicle body can be ensured. Furthermore, the side member according to the second configuration includes flanges. The flanges enhance rigidity against lateral bending deformation. More specifically, for example, if the ends of the upper and lower plates of a side member are free ends, when the side member undergoes lateral bending deformation, the unconstrained ends of the upper and lower plates and their vicinity buckle first. Therefore, improving the rigidity of the ends of the upper and / or lower plates of the side member directly leads to improving the rigidity of the entire side member with an open cross-section structure against lateral bending deformation. Specifically, by imparting some shape to the ends of the upper and / or lower plates of the side member, the local rigidity of the ends of the upper and / or lower plates can be enhanced. In this regard, in the side member according to the second configuration, a flange is provided on at least one of the upper and lower plates, thereby increasing the local rigidity of the ends of the upper and / or lower plates. As a result, the rigidity of the entire side member against lateral bending deformation is improved. In this case, when a load is input along the longitudinal direction of the vehicle body during a collision, lateral bending deformation is unlikely to occur and the reaction force is unlikely to decrease. This improves energy absorption, thereby ensuring crashworthiness.

[0018] In the first or second configuration, the maximum bending angle of the material constituting the side member at a plate thickness of 1.0 mm may be 40° or more (third configuration).

[0019] In the third configuration, the maximum bending angle of the material composing the side member at a plate thickness of 1.0 mm is 40° or more. In this case, even if the side member is bent and deformed, causing localized buckling, bending fracture at the buckled area can be suppressed. As a result, the reaction force during a collision is less likely to decrease compared to when bending fracture occurs, and a decrease in energy absorption can be suppressed.

[0020] In any one of the first to third configurations, the side member may have a Vickers hardness of 300 HV or more at the thickness center thereof (fourth configuration).

[0021] It is generally known that the Vickers hardness at the thickness center correlates with the tensile strength, which is the maximum stress in a tensile test. For example, a material with a Vickers hardness of 300 HV or more is a high-strength material with a tensile strength of 980 MPa or more. In the fourth configuration, the Vickers hardness at the thickness center of the side member is 300 HV or more. In other words, since the side member is made of a high-strength material with a relatively high tensile strength, the reaction force during a collision is large. Therefore, the side member according to the fourth configuration can improve the amount of energy absorption.

[0022] A vehicle body according to an embodiment includes a side member according to any one of the first to fourth configurations (fifth configuration).

[0023] 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.

[0024] 1 is a perspective view schematically showing a vehicle body 1 of an automobile or the like. The vehicle body 1 includes a side member 10 according to an embodiment. That is, the side member 10 is mounted on the vehicle body 1.

[0025] Referring to FIG. 1 , side members 10 are disposed on both the left and right sides of a vehicle body 1 and extend in the front-to-rear direction. When a vehicle or the like is involved in a front-to-rear collision, the side members 10 deform under a front-to-rear collision load and absorb the impact. In the present embodiment, the side members 10 are front side members. Therefore, one longitudinal end of each side member 10 is fixed to a bumper reinforcement 3 via a crash box 2. However, the side members 10 may also be rear side members or second members. The second members are members disposed vertically aligned with the front side members or rear side members.

[0026] Next, a detailed configuration of the side member 10 will be described. Hereinafter, the up-down direction when the side member 10 is attached to the vehicle body 1 may be simply referred to as the up-down direction. Similarly, the left-right direction when the side member 10 is attached to the vehicle body 1 may be simply referred to as the left-right direction, and the front-rear direction when the side member 10 is attached to the vehicle body 1 may be simply referred to as the front-rear direction.

[0027] 2 is a cross-sectional view (cross-sectional view taken along line II-II in FIG. 1) of the side member 10 according to the embodiment. The cross-section refers to a cross section perpendicular to the longitudinal direction of the side member 10. Referring to FIG. 2, the cross-sectional shape of the side member 10 is substantially U-shaped. The side member 10 includes an upper plate 11, a lower plate 12, and a side plate 13.

[0028] The upper plate 11 extends in the left-right direction in a cross-sectional view of the side member 10. The upper plate 11 may have a substantially flat shape in a cross-sectional view of the side member 10. In a cross-sectional view of the side member 10, the upper plate 11 may be parallel to the left-right direction or may be inclined. The inclination of the upper plate 11 with respect to the left-right direction is, for example, greater than or equal to −30° and less than +30°.

[0029] The lower plate 12 is disposed below the upper plate 11. The lower plate 12 is disposed so as to face the upper plate 11 in the up-down direction. The lower plate 12 extends in the left-right direction in a cross-sectional view of the side member 10. The lower plate 12 may have a substantially flat shape in a cross-sectional view of the side member 10. In a cross-sectional view of the side member 10, the lower plate 12 may be parallel to the left-right direction or may be inclined. The inclination of the lower plate 12 with respect to the left-right direction is, for example, greater than or equal to -30° and less than +30°. Furthermore, the lower plate 12 may be parallel to the upper plate 11 or may be inclined.

[0030] The side plates 13 extend in the up-down direction in a cross-sectional view of the side member 10. The side plates 13 may have a substantially flat shape in a cross-sectional view of the side member 10. In a cross-sectional view of the side member 10, the side plates 13 may be parallel to the up-down direction or may be inclined. The inclination of the side plates 13 with respect to the up-down direction is, for example, greater than or equal to −15° and less than +15°.

[0031] The side plate 13 connects the upper plate 11 and the lower plate 12 on one side in the left-right direction of the vehicle body 1 ( FIG. 1 ) so that an opening is formed between the upper plate 11 and the lower plate 12 on the other side in the left-right direction. In other words, the side member 10 has an open cross section. The cross section of the side member 10 is an open cross section not only before it is attached to the vehicle body 1 ( FIG. 1 ) but also after it is attached to the vehicle body 1. When the side member 10 is attached to the vehicle body 1, the opening between the upper plate 11 and the lower plate 12 is not closed by another member or the like.

[0032] The side members 10 open in the left-right direction of the vehicle body 1 ( FIG. 1 ). In the example of this embodiment, the side plates 13 are disposed inside the vehicle body 1 ( FIG. 1 ) in the left-right direction relative to the upper plate 11 and the lower plate 12. In this case, the side members 10 open on the outside of the vehicle body 1 ( FIG. 1 ) in the left-right direction. However, the opening direction of the side members 10 is not limited to this. The side members 10 may open on the inside of the vehicle body 1 ( FIG. 1 ) in the left-right direction. It is preferable that the side members 10 disposed on both the left and right sides of the vehicle body 1 shown in FIG. 1 have shapes that are symmetrical to each other in the left-right direction.

[0033] Referring again to FIG. 2 , the upper plate 11 is connected to the side plate 13 via a ridge portion 111. The upper plate 11 and the side plate 13 are each provided contiguous with the ridge portion 111. The ridge portion 111 is a corner portion between the upper plate 11 and the side plate 13. The ridge portion 111 is, for example, arc-shaped when viewed in cross section of the side member 10. When the ridge portion 111 is arc-shaped, the radius of curvature on the inner side of the bend of the ridge portion 111 is, for example, 1 mm or more and less than 50 mm. In this embodiment, the ridge portion 111 is provided at an end portion of the upper plate 11 that is on the inner side of the vehicle body 1 ( FIG. 1 ) in the left-right direction. An end portion 11a of the upper plate 11 opposite the side plate 13 in the left-right direction is open.

[0034] The lower plate 12 is connected to the side plate 13 via a ridge portion 121 on the opposite side of the upper plate 11. The lower plate 12 and the side plate 13 are each provided contiguous with the ridge portion 121. The ridge portion 121 is a corner portion between the lower plate 12 and the side plate 13. The ridge portion 121 is, for example, arc-shaped when viewed in cross section of the side member 10. When the ridge portion 121 is arc-shaped, the radius of curvature on the inner side of the bend of the ridge portion 121 is, for example, 1 mm or more and less than 50 mm. In this embodiment, the ridge portion 121 is provided at the end of the upper plate 11 that is on the inside of the vehicle body 1 ( FIG. 1 ) in the left-right direction. An end 12a of the lower plate 12 opposite the side plate 13 in the left-right direction is open.

[0035] The cross-sectional index I of the side member 10 is greater than 2.50. The cross-sectional index I is an index relating to the cross-sectional shape of the side member 10. When the length of the upper plate 11 is W1, the length of the lower plate 12 is W2, and the length of the side plate 13 is H, the cross-sectional index I is expressed as I = (W1 + W2) / H. If the length W1 of the upper plate 11 and the length W2 of the lower plate 12 are different, it is preferable that the shorter length of the upper plate 11 or the lower plate 12 is 0.3 times or more the longer length. The length W1 of the upper plate 11, the length W2 of the lower plate 12, and the length H of the side plate 13 can be measured on the cross-section of the side member 10. Note that when measuring the length of each plate, the shapes of holes, seats, beads, and the like partially formed in each plate are ignored.

[0036] The length W1 of the upper plate 11 means the linear distance from the intersection P of the imaginary lines L1 and L3 to the end 11a of the upper plate 11 in a cross-sectional view of the side member 10. The length W2 of the lower plate 12 means the linear distance from the intersection Q of the imaginary lines L2 and L3 to the end 12a of the lower plate 12 in a cross-sectional view of the side member 10. The length H of the side plate 13 means the linear distance from the intersection P to the intersection Q in a cross-sectional view of the side member 10. The imaginary line L1 is an extension of the outer surface of the upper plate 11. The imaginary line L2 is an extension of the outer surface of the lower plate 12. The imaginary line L3 is an extension of the outer surface of the side plate 13.

[0037] The side member 10 only needs to satisfy I>2.50 over its entire length in the longitudinal direction or at least a portion thereof. It is more preferable that within a range of 80% of the entire length in the longitudinal direction from the tip of the side member 10, for example, 20% or more of the entire length in the longitudinal direction, preferably 50% or more of the entire length in the longitudinal direction, of the cross section of the side member 10 satisfy I>2.50. The tip of the side member 10 is the end of both longitudinal ends that is located on the outer side in the fore-and-aft direction of the vehicle body 1 (FIG. 1), that is, the front end or the rear end of the vehicle body 1. Furthermore, it is preferable that the cross section index I is 8.00 or less.

[0038] The side member 10 is made of a metal plate. The side member 10 can be manufactured, for example, by press-forming a metal plate. The metal plate is preferably a steel plate. The thickness of the metal plate is, for example, 1.0 mm or more and 4.2 mm or less. The maximum bending angle of the material constituting the side member 10 at a plate thickness of 1.0 mm may be 40° or more. The maximum bending angle is determined by a bending test specified in VDA Standard 238-100 of the German Association of the Automotive Industry. The thickness of the sample used for the bending test must be 1.0 mm. The test piece for measuring the maximum bending angle is preferably cut from the center of one of the upper plate 11, lower plate 12, or side plate 13, which is as flat as possible. The size of this test piece is 60 mm long x 30 mm wide. If the test piece is thicker than 1.0 mm, one side is ground, and the test is performed so that the unground side is on the outer side of the bend in the bending test. It is generally known that the more homogenized the structure of a material, the larger the maximum bending angle.

[0039] The hardness (Vickers hardness) of the side member 10 is not particularly limited. In this embodiment, the Vickers hardness at the thickness center of the side member 10 is 300 HV or more. The Vickers hardness at the thickness center of the side member 10 can be calculated by a Vickers hardness test in accordance with JIS Z 2244:2009. Specifically, a sample is taken from a cross section of the side member 10 perpendicular to the longitudinal direction, near the center of the side plate 13, and the cross section is prepared as the measurement surface. The size and shape of the measurement surface are not particularly limited. To prepare the measurement surface, the measurement surface is polished using silicon carbide paper (sandpaper) with a grit size (roughness) of #600 to #1500. Then, the measurement surface is mirror-finished using a diluted solution such as alcohol or a liquid prepared by dispersing diamond powder with a particle size of 1 μm to 6 μm in pure water. Then, using a micro Vickers hardness tester, the Vickers hardness is measured at 10 points at a position 3 / 8 of the way down from the surface of the sample in the thickness direction, at intervals of at least three times the diagonal length of the indentation. The average value of these measurements is taken as the Vickers hardness at the center of the thickness of the side member 10. The test force is 300 gf (2.94 N).

[0040] [Effect] The cross-section index I of the side member 10 according to this embodiment is greater than 2.50. By increasing the cross-section index I of the side member 10, the second moment of area in the left-right direction of the vehicle body 1 can be increased. Therefore, when a load is input along the front-rear direction of the vehicle body 1 during a collision, lateral bending deformation is less likely to occur and the reaction force is less likely to decrease. This improves the amount of energy absorption, thereby ensuring collision resistance performance.

[0041] The side member 10 according to this embodiment does not require a separate member to close the opening, and therefore can be made lighter than a side member with a closed cross-section structure. Furthermore, the side member 10 according to this embodiment does not have a welded portion for joining to another member. In this case, naturally, the welded portion will not break during a collision. Therefore, the material of the side member 10 can be made stronger. Therefore, it is possible to reduce the weight while maintaining crashworthiness.

[0042] The side member 10 according to this embodiment has an open cross-sectional structure, which shortens its cross-sectional line length. Therefore, for the same plate thickness, the weight of the side member 10 is reduced compared to a conventional side member with a closed cross-sectional structure. The weight reduction in the side member 10 can be distributed to the plate thickness, making it possible to increase the plate thickness compared to a conventional side member with a closed cross-sectional structure. In this way, by increasing the plate thickness of the side member 10 in addition to satisfying the above-described condition for the cross-sectional index I, the crashworthiness of the side member 10 is more likely to be ensured and any reduction in the rigidity of the side member 10 is compensated for.

[0043] If the section index I is excessively large, the cross-sectional shape of the side member 10 becomes laterally flattened, making it more likely that bending deformation in the vertical direction will occur. Therefore, it is preferable that the section index I of the side member 10 is 8.00 or less. This makes it less likely that bending deformation in the vertical direction will occur when a collision load along the fore-and-aft direction of the vehicle body 1 is input to the side member 10, thereby making it possible to suppress a decrease in collision resistance performance.

[0044] In this embodiment, the maximum bending angle of the material constituting the side member 10 at a plate thickness of 1.0 mm is 40° or more. In this case, even if the side member 10 is bent and deformed, causing local buckling, bending fracture at the buckled portion can be suppressed. As a result, the reaction force during a collision is less likely to decrease compared to when bending fracture occurs, and therefore a decrease in the amount of energy absorption can be suppressed.

[0045] In this embodiment, the Vickers hardness at the thickness center of the side member 10 is 300 HV or more. In other words, since the side member 10 is made of a high-strength material with a relatively high tensile strength, the reaction force during a collision is large. Therefore, the side member 10 according to this embodiment can improve the amount of energy absorption.

[0046] Second Embodiment Fig. 3 is a cross-sectional view of a side member 10A according to a second embodiment. The side member 10A according to this embodiment differs from the side member 10 of the first embodiment in that it includes flanges 14, 15. The vehicle body 1 (Fig. 1) can be equipped with the side member 10A instead of the side member 10 of the first embodiment. Hereinafter, the up-down direction, left-right direction, and front-rear direction when the side member 10A is attached to the vehicle body 1 may be simply referred to as the up-down direction, left-right direction, and front-rear direction, respectively.

[0047] 3, in this embodiment, flanges are connected to both the upper plate 11 and the lower plate 12. Specifically, a flange 14 is connected to the upper plate 11, and a flange 15 is connected to the lower plate 12. In the example of FIG. 3, the flanges 14 and 15 protrude outward from the side member 10A.

[0048] The flange 14 extends in the up-down direction in a cross-sectional view of the side member 10A. The flange 14 may have a substantially flat shape in a cross-sectional view of the side member 10A. In a cross-sectional view of the side member 10A, the flange 14 may be parallel to the up-down direction or may be inclined. The inclination of the flange 14 with respect to the up-down direction is, for example, greater than or equal to −30° and less than +30°.

[0049] The flange 14 is connected to the upper plate 11 on the side opposite the side plate 13 and protrudes upward. The flange 14 is connected to the upper plate 11 via a ridge portion 112. The upper plate 11 and the flange 14 are each provided contiguous with the ridge portion 112. The ridge portion 112 is a corner portion between the upper plate 11 and the flange 14. The ridge portion 112 is, for example, arc-shaped when viewed in cross section of the side member 10A. When the ridge portion 112 is arc-shaped, the radius of curvature on the inner side of the bend of the ridge portion 112 is, for example, 1 mm or more and less than 50 mm. In this embodiment, the ridge portion 112 is provided at the end of the upper plate 11 that is outboard of the vehicle body 1 ( FIG. 1 ) in the left-right direction. The flange 14 protrudes upward from the ridge portion 112. An end 14a of the flange 14 opposite the upper plate 11 is open.

[0050] The flange 15 extends in the up-down direction in a cross-sectional view of the side member 10A. The flange 15 may have a substantially flat shape in a cross-sectional view of the side member 10A. In a cross-sectional view of the side member 10A, the flange 15 may be parallel to the up-down direction or may be inclined. The inclination of the flange 15 with respect to the up-down direction is, for example, greater than or equal to −30° and less than +30°.

[0051] The flange 15 is connected to the lower plate 12 on the side opposite the side plate 13 and protrudes downward. The flange 15 is connected to the lower plate 12 via a ridge portion 122. The lower plate 12 and the flange 15 are each provided contiguous with the ridge portion 122. The ridge portion 122 is a corner portion between the lower plate 12 and the flange 15. The ridge portion 122 is, for example, arc-shaped when viewed in cross section of the side member 10A. When the ridge portion 122 is arc-shaped, the radius of curvature on the inner side of the bend of the ridge portion 122 is, for example, 1 mm or more and less than 50 mm. In this embodiment, the ridge portion 122 is provided at the end of the lower plate 12 that is on the outer side of the vehicle body 1 ( FIG. 1 ) in the left-right direction. The flange 15 protrudes downward from the ridge portion 122. An end 15 a of the flange 15 opposite the lower plate 12 is open.

[0052] The cross-section index I of the side member 10A according to this embodiment is greater than 0.20. When the flange 14 is connected to the upper plate 11 as in this embodiment, the length W1 of the upper plate 11 refers to the linear distance from the intersection P of the imaginary lines L1 and L3 to the intersection R of the imaginary lines L1 and L4 in a cross-sectional view of the side member 10A. When the flange 15 is connected to the lower plate 12, the length W2 of the lower plate 12 refers to the linear distance from the intersection Q of the imaginary lines L2 and L3 to the intersection S of the imaginary lines L2 and L5 in a cross-sectional view of the side member 10A. The imaginary line L4 is an extension of the outer surface of the flange 14. The outer surface of the flange 14 refers to the surface of the flange 14 opposite the upper plate 11, of both surfaces in the left-right direction. The imaginary line L5 is an extension of the outer surface of the flange 15. The outer surface of the flange 15 refers to the surface of the flange 15 opposite the lower plate 12, of both surfaces in the left-right direction.

[0053] The lengths X1 and X2 of the flanges 14 and 15 are typically shorter than the length W1 of the upper plate 11 and the length W2 of the lower plate 12. The lengths X1 and X2 of the flanges 14 and 15 are, for example, 5 mm or more and less than 50 mm. When the end 14a of the flange 14 is open as in this embodiment, the length X1 of the flange 14 means the linear distance along the outer surface of the flange 14 from the intersection R of the imaginary lines L1 and L4 to the end 14a. When the end 15a of the flange 15 is open, the length X2 of the flange 15 means the linear distance along the outer surface of the flange 15 from the intersection S of the imaginary lines L2 and L5 to the end 15a.

[0054] The cross-section index I of the side member 10A according to this embodiment is greater than 0.20. Therefore, a certain degree of cross-sectional moment of inertia in the left-right direction of the vehicle body 1 can be ensured. Furthermore, the side member 10A according to this embodiment is provided with flanges 14, 15. The flanges 14, 15 increase rigidity against lateral bending deformation. In this case, when a load is input along the fore-and-aft direction of the vehicle body 1 (FIG. 1) during a collision, lateral bending deformation is unlikely to occur and the reaction force is unlikely to decrease. As a result, the side member 10A according to this embodiment can improve energy absorption, thereby ensuring collision resistance performance.

[0055] In this embodiment, too, the maximum bending angle of the material constituting the side member 10A at a plate thickness of 1.0 mm is preferably 40° or greater. Furthermore, the Vickers hardness of the side member 10A at the center of its thickness is preferably 300 HV or greater. This allows the side member 10A to maintain a satisfactory energy absorption capacity, similar to the first embodiment.

[0056] The side member 10A according to this embodiment has an open cross-sectional structure similar to the side member 10 according to the first embodiment. That is, the side member 10A opens to the outside or inside of the vehicle body 1 ( FIG. 1 ) in the left-right direction. The side member 10A has an open cross-sectional structure, which shortens its cross-sectional line length. Therefore, for the same plate thickness, the weight of the side member 10A is reduced compared to a conventional side member having a closed cross-sectional structure. As with the first embodiment, the side member 10A may be increased by allocating the weight reduction to the plate thickness. Increasing the plate thickness of the side member 10A in addition to satisfying the condition of the cross-sectional index I makes it easier to ensure the crashworthiness of the side member 10A and compensates for any reduction in the rigidity of the side member 10A.

[0057] 4 and 5 are cross-sectional views of a side member 10A according to a modified example of this embodiment. In the example shown in FIG. 3, the flanges 14, 15 protrude outward from the side member 10A. That is, the flange 14 protrudes upward from the upper plate 11, and the flange 15 protrudes downward from the lower plate 12. However, as shown in FIG. 4, the flanges 14, 15 may protrude inward from the side member 10A in a cross-sectional view of the side member 10A. In the example shown in FIG. 4, the flange 14 protrudes downward from the upper plate 11, and the flange 15 protrudes upward from the lower plate 12. Also, in the example shown in FIG. 3, the flanges 14, 15 are connected to the upper plate 11 and the lower plate 12, respectively. However, as shown in FIG. 5, in the side member 10A, the flange 14 may be connected to the upper plate 11, and no flange may be connected to the lower plate 12. Conversely, in the side member 10A, the flange 15 (FIGS. 3 and 4) may be connected to the lower plate 12, and no flange may be connected to the upper plate 11. Even in this case, the flange 14 or 15 may protrude either upward or downward. Furthermore, the shapes of the flanges 14, 15 are not limited to the examples shown in FIGS. 3 to 5. For example, another plate may be connected to the flanges 14, 15 via a ridge portion.

[0058] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to the following examples.

[0059] In order to confirm the effects of the present disclosure, FEM analysis was performed on the side member using general-purpose crash analysis software (LS-DYNA) to examine its energy absorption performance. In the analysis, the front side member 10, crash box 2, and bumper reinforcement 3 shown in FIG. 1 were modeled using shell elements. Then, with the rear end of the front side member 10 fully restrained, a rigid wall was caused to collide with the bumper reinforcement 3 from the front to the rear of the vehicle at 50 km / h. The amount of energy absorption was measured from the collision reaction force while the rigid wall moved 450 mm.

[0060] In this analysis, a conventional side member was used as a control, and the energy absorption amount (absorbed energy ratio) relative to the control was calculated. Figure 6 shows an analytical model of the side member 10 used as the control. Figure 7 is a cross-sectional view taken along line VII-VII in Figure 6. As shown in Figure 7, the control side member 10 had a closed cross-sectional structure in which a member main body 20 with a generally hat-shaped cross section and a closing plate 30 were joined. The control side member 10 had a plate thickness of 1.6 mm and a Vickers hardness of 270 Hv at the center of the thickness. In the member main body 20, the length W1 of the upper plate 11 and the length W2 of the lower plate 12 were 60 mm, the length H of the side plate 13 was 140 mm, and the lengths X1 and X2 of the flanges 14 and 15 were 20 mm. The length Y of the closing plate 30 was 180 mm. The flanges 14 and 15 of the member main body 20 and the closing plate 30 were joined by spot welding at 30 mm intervals. The side member of Comparative Example 1 had the same basic structure as the control side member 10. However, the side member of Comparative Example 1 had a higher Vickers hardness and a smaller plate thickness than the control side member 10.

[0061] FIG. 8 is a diagram showing an example of an analytical model of the side members 10 of Examples 1 to 8 and Comparative Examples 2 to 4. The side members 10 of Examples 1 to 8 and Comparative Examples 2 to 4 all had an open cross-section structure. Among Examples 1 to 8 and Comparative Examples 2 to 4, the side member 10 of Example 3 opened on the inner side in the left-right direction of the vehicle body, while the others opened on the outer side in the left-right direction. The side members 10 of Examples 1 to 3 and Comparative Examples 2 and 3 all had the basic configuration shown in FIG. 2. The side members 10 of Examples 4 to 5 and 8 and Comparative Example 4 all had the basic configuration shown in FIG. 3. The side member 10 of Example 6 had the basic configuration shown in FIG. 4. The side member 10 of Example 7 had the basic configuration shown in FIG. 5. The cross-section index I of each side member 10 was changed as appropriate. Specifically, the length W1 of the upper plate 11, the length W2 of the lower plate 12, and the length H of the side plate 13 of each side member 10 were changed as appropriate. The analytical specifications and results are shown in Table 1. An absorbed energy ratio of 1.00 or more means that the crashworthiness is equal to or better than that of the control side member 10. Therefore, in the test results in Table 1, if the absorbed energy ratio is 1.00 or more, it is indicated as "excellent," and if not, it is indicated as "poor." The analysis results are also shown in Figures 9 and 10.

[0062]

[0063] As described above, the Vickers hardness of the side member 10 of the control example was 270 HV. Because the strength of the material of the side member 10 of the control example was relatively low, no fracture occurred in the welded portion during a collision. Therefore, when subjected to a collision load, deformation progressed while maintaining a closed cross section, and high load-bearing performance was obtained.

[0064] The side member of Comparative Example 1 has the same closed cross-sectional structure as the control example, but its plate thickness was reduced by increasing the Vickers hardness, resulting in a weight reduction compared to the control example. The side members 10 of Examples 1 to 7 and Comparative Examples 2 to 4 have an open cross-sectional structure and a short cross-sectional line length, resulting in a weight reduction despite an increased plate thickness. The weight ratio of the side members 10 of Examples 1 to 7 and Comparative Examples 1 to 4 to the control example was all 0.875. Therefore, a weight reduction of 12.5% ​​was achieved compared to the side member 10 of the control example.

[0065] However, since the side member of Comparative Example 1 had a higher Vickers hardness than the side member 10 of the Control Example, many fractures occurred in the welded joints during a collision. As a result, the closed cross section formed by the member main body 20 and the closing plate 30 could not be maintained, and the reaction force during a collision was significantly reduced. As a result, the absorbed energy ratio was less than 1.00.

[0066] The side members 10 of Comparative Examples 2 and 3 all had an open cross-section structure and therefore did not have welds. However, the cross-section index I of the side members 10 of Comparative Examples 2 and 3 was 2.50 or less. In other words, the length W1 of the upper plate 11 and the length W2 of the lower plate 12 relative to the length H of the side plate 13 were insufficient. As a result, the cross-section opened early when subjected to a collision load, causing bending deformation and a significant decrease in reaction force, resulting in an absorbed energy ratio of less than 1.00.

[0067] The side members 10 of Examples 1 to 3 all had an open cross-section structure and therefore did not have welds. Furthermore, the cross-section index I of the side members 10 of Examples 1 to 3 was all greater than 2.50. Therefore, the absorbed energy ratio was 1.00 or greater. In particular, the results of Example 3 showed that collision resistance performance could be ensured even when the opening of the side member 10 with an open cross-section structure was directed inward in the left-right direction of the vehicle body.

[0068] The side member 10 of Comparative Example 4 had a flange. However, the cross-section index I of the side member 10 of Comparative Example 4 was 0.20 or less. As a result, bending deformation occurred in the direction in which the opening of the side member 10 increased, which significantly reduced the crashworthiness, and the absorbed energy ratio became less than 1.00.

[0069] The side members 10 of Examples 4 to 8 all had flanges. Furthermore, the cross-sectional index I of the side members 10 of Examples 4 to 8 was all greater than 0.20. As a result, the absorbed energy ratio was 1.00 or greater. This shows that a side member 10 having a flange can ensure collision resistance if its cross-sectional index I is greater than 0.20. In particular, the results of Example 6 show that collision resistance can be ensured even if the flange protrudes toward the inside of the side member 10. Furthermore, the results of Example 7 show that collision resistance can be ensured even if a flange is connected to only one of the upper plate 11 and the lower plate 12.

[0070] The side member 10 of Example 8 had a higher Vickers hardness than those of Examples 4 to 7, and therefore was able to achieve an absorbed energy ratio of 1.00 or more even with a relatively smaller plate thickness. As a result, the weight ratio compared to the side member 10 of the control example was 0.760, achieving a weight reduction of 24.0%.

[0071] The bendability of the steel plates used for the side members 10 of Examples 1 to 8 and Comparative Examples 1 to 4, i.e., the maximum bending angle at a plate thickness of 1.0 mm, was 40° or greater in all cases. Therefore, bending fracture did not occur at the locations where local buckling occurred due to bending deformation of the side members 10. Therefore, a decrease in reaction force due to bending fracture did not occur, and a decrease in energy absorption capacity could be suppressed.

[0072] 1: Vehicle body 10, 10A: Side member 11: Upper plate 12: Lower plate 13: Side plate 14, 15: Flange

Claims

1. A side member for a vehicle body, comprising: an upper plate; a lower plate that is disposed below the upper plate when the side member is attached to the vehicle body; and a side plate that connects the upper plate and the lower plate on one side of the vehicle body in the left-right direction so that an opening is formed between the upper plate and the lower plate on the other side of the vehicle body in the left-right direction when the side member is attached to the vehicle body, wherein, in a cross-sectional view of the side member, where the length of the upper plate is W1, the length of the lower plate is W2, and the length of the side plate is H, a cross-sectional index I expressed as I = (W1 + W2) / H is greater than 2.

50.

2. A side member for a vehicle body, comprising: an upper plate; a lower plate disposed below the upper plate when the side member is attached to the vehicle body; a side plate connecting the upper plate and the lower plate on one side in the left-right direction of the vehicle body so that an opening is formed between the upper plate and the lower plate on the other side in the left-right direction when the side member is attached to the vehicle body; and a flange connected to at least one of the upper plate and the lower plate on the side opposite to the side plate and protruding upward or downward, wherein, in a cross-sectional view of the side member, where W1 is the length of the upper plate, W2 is the length of the lower plate, and H is the length of the side plate, a cross-sectional index I expressed as I = (W1 + W2) / H is greater than 0.

20.

3. A side member according to claim 1 or 2, wherein the maximum bending angle of the material constituting said side member at a plate thickness of 1.0 mm is 40° or more.

4. A side member according to claim 1 or 2, wherein the Vickers hardness at the thickness center of the side member is 300 HV or more.

5. A vehicle body comprising the side member according to claim 1 or 2.

Images