JP7288183B2 - body parts - Google Patents

Description

The present invention relates to a body member, for example for motor vehicles.

2. Description of the Related Art Conventionally, a hollow member made of a steel plate and having a predetermined cross-sectional shape is used as a vehicle body member. These vehicle body members are required to be lightweight and have sufficient load resistance. For this reason, in recent years, high-strength steel sheets have been used as materials in some cases.

When an impact such as a collision is applied to the vehicle body, the vehicle body member may receive an axial compressive load. In order to achieve a sufficient load bearing capacity of the vehicle body member, it is required to secure a high axial compressive strength of the vehicle body member, for example, to suppress buckling. In Patent Document 1 below, in order to realize a member for body structure that is subjected to axial compressive bending deformation, in order to realize a member that is lighter and has high axial compressive bending strength, the surface that undergoes compressive deformation is curved outwardly. technique is described.

JP 2005-186777 A

In the technique described in Patent Document 1, of the cross-sectional shape of the member, only the shape of the surface that undergoes compression deformation is curved outward, and the cross-sectional shape including the plane that is continuous with the curved surface is the entire member. The effect on axial compressive strength is not considered. Further, reduction in thickness and increase in strength of materials used for vehicle body structural members can reduce the elastic buckling stress of the members. For this reason, elastic buckling may occur before the yield stress of the material is reached at the portion receiving the axial compressive load, which may reduce the axial compressive strength. However, the conventional techniques, including the technique described in Patent Document 1, do not set the cross-sectional shape of the vehicle body member from such a viewpoint.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved vehicle body member that is lighter in weight and capable of ensuring high axial compressive strength. to do.

In order to solve the above problems, according to one aspect of the present invention, at least one curved portion is formed of a steel plate having a thickness of 1.6 mm or less and has a cross-sectional shape in the direction perpendicular to the axis that is outwardly or inwardly convex. and at least one flat portion, and one curved portion having the largest radius of curvature is defined as the reference curved portion, and when the flat portion continues to only one of the longitudinal ends of the reference curved portion, the plane If the plane portions are continuous at both ends, the longer plane portion of the plane portions is used as the reference plane portion, and the reference curve is started from the end of the longitudinal direction end of the reference curved portion where the reference plane portion is not continuous. A straight line extending in a tangential direction of the portion is defined as a first straight line, an extension line of the reference flat portion is defined as a second straight line, and the intersection of the first straight line and the second straight line is connected to the reference curved portion of both ends in the longitudinal direction of the reference flat portion. The following equations (1) and (2) are satisfied, where b0 is the length between the opposite end and b0, b1 is the length of the reference flat portion, and R is the radius of curvature of the reference curved portion. A vehicle body member selected from a tunnel, a kick reinforcement, a floor cross member, and an under reinforcement is provided, in which the steel plate has a tensile strength of 1180 MPa or more and an R of 15 mm or more . However, the thickness of the steel plate forming the reference flat portion is t, Young's modulus is E, Poisson's ratio is ν, and yield stress is _σy .

The b1 may be 10 mm or more.

An angle formed by the first straight line and the second straight line with the reference curved portion interposed therebetween may be 80° or more and 150° or less.

The cross section perpendicular to the axis may be a closed cross section.

As described above, according to the present invention, there is provided a vehicle body member that is lighter in weight and capable of ensuring a high axial compressive strength.

1 is an axis-perpendicular cross-sectional view showing an example of a vehicle body member according to a first embodiment of the present invention; FIG. 4 is a graph showing the relationship between the curvature radius of the reference curved portion of the vehicle body member according to Example 1-1 and the axial compressive strength. 10 is a graph showing the relationship between the curvature radius of the reference curved portion of the vehicle body member according to Example 1-2 and the axial compressive strength. FIG. 11 is a cross-sectional view in the direction perpendicular to the axis showing a vehicle body member according to modification 1-1 of the first embodiment; FIG. 11 is a cross-sectional view in the direction perpendicular to the axis showing a vehicle body member according to Modification 1-2 of the same embodiment. FIG. 11 is a cross-sectional view in the direction perpendicular to the axis showing a vehicle body member according to Modified Example 1-3 of the same embodiment; FIG. 5 is an axis-perpendicular cross-sectional view showing an example of a vehicle body member according to a second embodiment of the present invention; FIG. 11 is a cross-sectional view in the direction perpendicular to the axis showing a vehicle body member according to modification 2-1 of the same embodiment; FIG. 11 is a cross-sectional view in the direction perpendicular to the axis showing a vehicle body member according to modification 2-2 of the same embodiment. FIG. 11 is a cross-sectional view in the direction perpendicular to the axis showing a vehicle body member according to Modification 2-3 of the same embodiment; FIG. 11 is a cross-sectional view in the direction perpendicular to the axis showing a vehicle body member according to Modified Example 2-4 of the same embodiment; It is a figure which shows the motor vehicle skeleton as an example to which the vehicle body member which concerns on embodiment is applied.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

<First Embodiment>
First, the configuration of the first embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view showing an example of a vehicle body member according to this embodiment. The vehicle body member 1 may be a structural member of a vehicle body, in other words a skeleton member. The bodywork may be, for example, the bodywork of an automobile. The vehicle body member 1 is, for example, a hollow tubular member made of a steel plate. Hereinafter, the longitudinal direction along the axis of the vehicle body member 1 will also be referred to as the axial direction. The steel plate that is the material of the vehicle body member 1 is not particularly limited, but the tensile strength thereof may be 1180 MPa or more. The tensile strength is not limited to 1.2 GPa class, and may be 1.5 GPa class, 1.8 GPa class, 2.5 GPa class, or the like. When the plate thickness of the steel plate is 1.6 mm or less, the vehicle body member 1 according to the present embodiment exhibits the effects described later. Note that the thickness of the steel plate may be, for example, 0.4 mm or more from the viewpoint of impact absorption properties required for the vehicle body member 1 . The vehicle body member 1 can be formed by applying various known processing techniques to steel plates. As an example, the vehicle body member 1 may be formed by forming a blank material into a predetermined shape by cold drawing press working. Also, the vehicle body member 1 may be formed by hot stamping, for example.

The vehicle body member 1 may be in the shape of a square tube, for example. FIG. 1 shows a cross-section perpendicular to the axial direction (axis-perpendicular cross-section) of a square tubular body member 1 . A cross section of the vehicle body member 1 perpendicular to the axis is a closed cross section, and has four curved portions 100, 101, 102, and 103 and four flat portions 110, 111, 112, and 113. As shown in FIG. The curved portions 100 , 101 , 102 , 103 are arcuately convex outwardly of the vehicle body member 1 and may have the same shape and size. The planar portions 110, 111, 112, 113 may be linear and of the same size.

Of the curved portions 100 , 101 , 102 and 103 , one curved portion having the largest radius of curvature is defined as a reference curved portion 10 . Here, the radius of curvature of the curved portion is obtained, for example, as follows. That is, in the cross section in the axis-perpendicular direction, the two R stop points that are the starting point or the end point of the bending of the steel plate on the surface of the vehicle body member 1 (in other words, the boundary point between the curved line and the straight line), Find three points: the bend center point equidistant along the surface from one R stop point. By determining the curvature from these three points by a known mathematical method, the radius of curvature of the curved portion can be obtained. In addition, the said surface is the surface of the bending outer side of a steel plate, as shown in FIG. In the example shown in FIG. 1, since the curved portions 100, 101, 102, and 103 have the same radius of curvature, the curved portion 100 can be used as the reference curved portion 10, for example. Also, let R be the radius of curvature of the reference curved portion 10 .

Flat portions 110 and 113 are continuous with both ends P and Q of the reference curved portion 10 in the longitudinal direction, respectively, in the cross section in the direction perpendicular to the axis. These ends P and Q are the two R stop points on the surface of the body member 1 . The longer plane portion of the plane portions 110 and 113 is defined as the reference plane portion 11 . In the example shown in FIG. 1, since the plane portions 110 and 113 have the same length, the plane portion 110 can be used as the reference plane portion 11, for example. If a plane portion continues to only one of the longitudinal ends P and Q of the reference curved portion 10 , the plane portion may be used as the reference plane portion 11 .

A straight line extending in the tangential direction of the reference curved portion 10 from the end P of the longitudinal direction ends P and Q of the reference curved portion 10 at which the reference plane portion 11 is not continuous, in other words, a tangent to the surface of the reference curved portion 10 at the end P , the first straight line L1. Further, an extension line of the surface of the reference plane portion 11 (in the example shown in FIG. 1, the surface that is continuous with the surface of the bending outer side of the reference curved portion 10) is defined as a second straight line L2.

Let b0 be the length between the intersection point S of the first straight line L1 and the second straight line L2 and the end T of the longitudinal direction ends Q and T of the reference flat portion 11 that is not connected to the reference curved portion 10 .

Let θ be the angle formed by the first straight line L1 and the second straight line L2 with the reference curved portion 10 interposed therebetween. θ may be set within a range of 80° or more and 150° or less. In the example shown in FIG. 1, θ is set at or near 90°.

Let b1 be the length (width), t be the plate thickness, E be the Young's modulus, ν be the Poisson's ratio, and _σy be the yield stress of the reference plane portion 11 in the cross section in the direction perpendicular to the axis. At this time, the curvature radius R of the reference curved portion 10 is set so as to satisfy the following formula (1). For example, when the tensile strength of the steel plate used as the material is 1180 MPa or more, the radius of curvature R set in this manner may be 15 mm or more. Also, the upper limit of the radius of curvature R is not particularly limited, and may be any radius of curvature that makes the length b1 of the reference plane portion 11 greater than zero, as will be described later.

The length b1 of the reference plane portion 11 is set so as to satisfy the following formula (2). Note that the length b1 set in this way may be, for example, 10 mm or more within the range that satisfies the formula (2).

Next, the effects of this embodiment will be described. An axial compressive load (axial compressive load) can act on the vehicle body member 1 . Of the vehicle body member 1, portions corresponding to the curved portions 100 to 103 have higher rigidity against an axial compressive load than portions corresponding to the flat portions 110 to 113 due to their shape. Hard to bend. Therefore, the curvature radius R of the reference curved portion 10 is set to a predetermined value or more. As a result, even if one of the plane portions on both sides of the reference bending portion 10 (for example, the plane portion 110) tries to elastically buckle, the deformation exerts on the other (for example, the plane portion 113). jointly trying to elastically buckle can be blocked by the reference curved portion 10 . Therefore, the vehicle body member 1 as a whole can suppress elastic buckling and improve the axial compressive strength. Specifically, by setting the radius of curvature R of the reference curved portion 10 to be equal to or greater than the lower limit defined by the left side of the above equation (1), the above influence is suppressed, and the elastic buckling of the entire vehicle body member 1 is suppressed. can be suppressed. The curvature radius R may be, for example, 15 mm or more when the tensile strength of the steel plate is 1180 MPa or more. See Example 1-1).

Further, by setting the length b1 of the reference plane portion 11 to be equal to or less than the upper limit defined by the right side of the above equation (2), it is possible to suppress elastic buckling of the plane portion continuing to the reference bending portion 10 . Formula (2) is a formula obtained as a result of extensive studies by the present inventors. Using the equation (2), the effective maximum length of the flat portion is calculated in consideration of the deformation mode against the axial compressive load of the vehicle body member 1 formed of high-strength and small-thickness steel plate. Here, the effective maximum length is defined as such that the elastic buckling stress is equal to or higher than the yield stress in a predetermined range (for example, the entire range) in the longitudinal direction of the flat portion in the cross section in the direction perpendicular to the axis, thereby avoiding elastic buckling. This is the upper limit of the length of the flat portion.

By setting the length b1 of the reference flat portion 11 to be equal to or less than the effective maximum length, elastic buckling is suppressed in a predetermined range (for example, the entire range) of the reference flat portion in the longitudinal direction. In other words, until the axial compressive stress reaches the strength limit of the material within a predetermined range in the longitudinal direction of the reference flat portion, the load applied to the reference flat portion is absorbed by the strength of the material. less likely to be converted to elastic buckling; Of the two flat portions sandwiching the reference curved portion on both sides, the length of the flat portion on the side opposite to the reference flat portion is equal to or shorter than the length of the reference flat portion according to the definition of the reference flat portion. Therefore, since the length of this flat portion is also equal to or less than the upper limit defined by the right side of the above equation (2), elastic buckling is suppressed even in this flat portion. In other words, elastic buckling is suppressed in the flat portions on both sides of the reference curved portion.

The lower limit of the radius of curvature R defined by the left side of the above equation (1) is the length b0 minus the maximum effective length of the planar portion. In other words, the lower limit of the curvature radius R is set so that the curvature radius R of the reference curved portion can be secured as large as possible while keeping the length of the reference flat portion equal to or less than the effective maximum length. Therefore, elastic buckling can be suppressed in the flat portions on both sides of the reference curved portion, and even if one of these flat portions tries to buckle, the other flat portion will not be affected by the buckling of both flat portions. Intervening reference bends can provide blocking. Thus, the synergistic effect of the lower limit value of the radius of curvature R and the upper limit value of the length b1 makes it possible to improve the axial compressive strength and suppress elastic buckling of the vehicle body member 1 as a whole.

The angle θ between the first straight line L1 and the second straight line L2 may be 80° or more and 150° or less. When the angle θ is 150° or less, the longitudinal end of the flat portion in the cross section in the direction perpendicular to the axis is supported by other portions at a certain angle. be able to. Therefore, the definition of the effective maximum length of the reference flat portion according to the above formula (2) functions effectively, and the above effect can be effectively obtained when the length b1 satisfies the formula (2). Further, when the angle θ is 80° or more, it becomes easy for the curvature radius R of the reference curved portion to satisfy the formula (1).

The vehicle body member 1 is formed of a steel plate having a tensile strength of a predetermined value or more and a plate thickness of a predetermined value or less. In this way, by thinning and increasing the strength of the material used for the vehicle body member 1, the weight of the vehicle body member 1 can be reduced and the load resistance can be improved. However, thinning and increasing the strength of the material of the vehicle body member 1 can reduce the elastic buckling stress of the planar portion of the member. That is, the elastic buckling stress of the flat portion is greatly reduced due to the reduction in the plate thickness t of the flat portion. Further, even if the strength of the flat portion against the axial compressive load is the same, as can be seen from the right side of the above equation (2), the smaller the plate thickness t and the larger the yield stress _σy , the greater the strength of the flat portion. Effective maximum length becomes smaller. Therefore, if no consideration is given to the length of the flat portion in the direction perpendicular to the axis, there is a high possibility that elastic buckling will occur before the yield stress of the material is reached at the portion receiving the compressive load.

On the other hand, by setting the length b1 of the reference plane portion 11 to be equal to or less than the upper limit value (maximum effective length) defined by the right side of the above equation (2), even if the material is made thinner and stronger, Elastic buckling of the plane portion can be suppressed. Further, by setting the curvature radius R of the reference curved portion 10 to be equal to or greater than the lower limit defined by the left side of the above formula (1), even if the material is thinned and strengthened, the vehicle body member 1 as a whole can be improved. Elastic buckling can be effectively suppressed. Specifically, the vehicle body member 1 is made of a steel plate having a thickness of 1.6 mm or less. Due to such plate thickness, the problem of reduction in elastic buckling stress as described above is likely to occur. On the other hand, by setting the curvature radius R or the length b1 using the above formulas (1) and (2), a remarkable effect can be obtained. Moreover, the vehicle body member 1 may be formed of a steel plate having a tensile strength of 1180 MPa or more, for example. In the case of such tensile strength, the problem of a decrease in elastic buckling stress as described above is likely to occur. By doing so, a remarkable effect can be obtained.

By setting the length b1 of the reference flat portion 11 to a value larger than the lower limit defined by the left side of the above equation (2), the rigidity of the vehicle body member 1 against bending and twisting can be improved. That is, as shown in FIG. 1, the distance d0 from the neutral axis N to the plane portion 110 is greater than the distance d1 (moment arm around the neutral axis N) from the neutral axis N of the vehicle body member 1 to the curved portions 100 and 101. (moment arm about neutral axis N) is larger. Therefore, by setting the length b1 of the reference flat portion 11 to be greater than 0, in other words, by providing the flat portion on the vehicle body member 1, a relatively small vibration of the vehicle body member 1 when the vehicle body vibrates or runs over a curb is reduced. It is possible to improve the compressive strength against bending and torsion (small load) caused by From this point of view, the length b1 should be as large as possible within the range of the maximum effective length of the plane portion. By increasing the length b1, that is, by increasing the proportion of the flat portion in the cross-sectional shape of the vehicle body member 1, the rigidity can be further improved.

The length b1 of the reference plane portion 11 may be equal to or greater than a predetermined lower limit value greater than zero. In this case, the maximum load capacity of the compression surface (for example, on the bending side) of the vehicle body member 1 can be increased when a large load is input, so the energy absorption amount of the vehicle body member 1 can be increased. That is, when the cross section of the vehicle body member 1 in the direction perpendicular to the axis is made up of a flat portion as well, compared to the case where it is made up of only a curved portion (circular shape, etc.), the above cross section is better when compared in the same design space. , ie the cross-sectional area A can be increased. The strength of the vehicle body member 1 is proportional to the product of the yield stress σ _y and the cross-sectional area A of the material. By increasing the cross-sectional area A, the maximum load resistance (axial compressive strength) of the compression surface of the vehicle body member 1 can be increased, so that the energy absorption amount of the vehicle body member 1 can be increased. The lower limit value of the length b1 can be set based on the relationship between the thickness t of the steel plate that is the material of the vehicle body member 1 and the yield stress _σy . For example, the length b1 may be 10 mm or more. This value of 10 mm is a value that can be selected as the above-mentioned lower limit suitable for suppressing an excessive decrease in the cross-sectional area A when, for example, the thickness of the steel plate is t = 0.5 mm and σ _y = 2 GPa. .

[Example]
The present inventors applied an axial compressive load to the specimens (Examples 1-1 and 1-2) having the cross-sectional shape (angle θ = 90°) shown in Fig. 1, and found that the curvature of the reference curved portion The relationship between the radius R (mm) and the axial compressive strength P (kN) of the specimen was investigated. The test piece of Example 1-1 had an axial dimension of 288 mm and an outer dimension D of 72 mm. 1256 MPa, yield stress was 943 MPa. The test results of Example 1-1 are shown in Table 1 together with the length b0, the length b1, the left side of Equation (1) and the right side of Equation (2) (ie, the effective maximum length of the flat portion).

The specimen of Example 1-2 had an axial dimension of 480 mm and an outer dimension D of 120 mm. 431 MPa, yield stress was 319 MPa. The test results of Example 1-2 are shown in Table 2 together with the length b0, the length b1, the left side of Equation (1) and the right side of Equation (2) (ie, the effective maximum length of the flat portion).

When the radius of curvature R of the reference curved portion is small, the lengths b0 and b1 are large and the left side of Equation (1) is large. Therefore, when R is less than a certain threshold value R*, R is less than the left side of equation (1), and equation (1) does not hold. Also, when R is less than R*, b1 is greater than the right side of equation (2), and equation (2) does not hold. On the other hand, when R is large, b0 and b1 are small and the left side of equation (1) is small. Therefore, when R is equal to or greater than the threshold R*, R is equal to or greater than the left side of Equation (1), and Equation (1) holds. Also, when R is equal to or greater than the threshold value R*, b1 is equal to or less than the right side of Equation (2), and Equation (2) holds. In Example 1-1, the right side of formula (2) was 45.0 mm and R* was 13.5 mm. In Example 1-2, the right side of equation (2) was 77.3 mm and R* was 21.4 mm.

FIG. 2 graphically represents the test results of Example 1-1. When the radius of curvature R of the reference curved portion is equal to or less than a predetermined value (=24 mm), the axial compressive strength P is less than 315 kN, which is small, in the range where the radius of curvature R is less than the threshold value R* (=13.5 mm). . It is considered that this is because the equations (1) and (2) do not hold, so that the planar portions sandwiching both sides of the curved portion are likely to interact with each other, and elastic buckling is likely to occur. In the range where the curvature radius R was R* (=13.5 mm) or more, the axial compressive strength P was 315 kN or more, which was large. It is considered that this is because the expressions (1) and (2) hold, so that the interaction is suppressed and the occurrence of elastic buckling is suppressed. Note that when the radius of curvature R exceeded a predetermined value (=24 mm), the axial compressive strength P decreased as the radius of curvature R increased. It is considered that this is because the cross-sectional area decreased due to the decrease in the proportion of the flat portion in the cross-sectional shape.

FIG. 3 graphically represents the test results of Examples 1-2. When the radius of curvature R of the reference curved portion is equal to or less than a predetermined value (=40 mm), the axial compressive strength P is less than 197 kN in the range where the radius of curvature R is less than the threshold value R* (=21.4 mm). . It is considered that this is because the equations (1) and (2) do not hold, so that the planar portions sandwiching both sides of the curved portion are likely to interact with each other, and elastic buckling is likely to occur. In the range where the curvature radius R was R* (=21.4 mm) or more, the axial compressive strength P was 197 kN or more, which was large. It is considered that this is because the expressions (1) and (2) hold, so that the interaction is suppressed and the occurrence of elastic buckling is suppressed. Note that when the radius of curvature R exceeded a predetermined value (=40 mm), the axial compressive strength P decreased as the radius of curvature R increased. It is considered that this is because the cross-sectional area decreased due to the decrease in the proportion of the flat portion in the cross-sectional shape.

In Example 1-1, compared with Example 1-2, not only was a large axial compressive strength P obtained in the range of the curvature radius R equal to or greater than the threshold value R*, The amount of increase in the directional compressive strength P was large. This is because in Example 1-1, a steel plate having a tensile strength of 1180 MPa or more was used, so the curvature radius R was set using formula (1), or the length b1 was set using formula (2) It is believed that this is because the above-mentioned effects could be obtained more remarkably than in Example 1-2.

[Modification 1-1]
FIG. 4 shows a modification of the cross-sectional shape shown in FIG. The curvature radii of the curved portions 102 and 103 are the same, and the curvature radius of the curved portion 100 is larger than the curvature radius of the curved portion 103 . Since the curved portions 100 and 101 have the same radius of curvature, the curved portion 100 may be used as the reference curved portion 10, for example. The longer planar portion 110 of the planar portions 110 and 111 that are continuous with both ends in the longitudinal direction of the reference curved portion 10 is referred to as the reference planar portion 11 . If the curvature radius R of the reference curved portion 10 satisfies the formula (1) and the length b1 of the reference flat portion 11 satisfies the formula (2), the same effect as the example shown in FIG. 1 can be obtained. can get. For example, the radius of curvature R may be 15 mm or more and the length b1 may be 10 mm or more.

[Modification 1-2]
FIG. 5 shows a modification of the cross-sectional shape shown in FIG. The curvature radii of the curved portions 102 and 103 are the same, and the curvature radius of the curved portion 100 is larger than the curvature radius of the curved portion 103 . Since the curved portions 100 and 101 have the same radius of curvature, the curved portion 100 may be used as the reference curved portion 10, for example. The longer planar portion 110 of the planar portions 110 and 113 that are continuous with both ends in the longitudinal direction of the reference curved portion 10 is referred to as the reference planar portion 11 . If the curvature radius R of the reference curved portion 10 satisfies the formula (1) and the length b1 of the reference flat portion 11 satisfies the formula (2), the same effect as the example shown in FIG. 1 can be obtained. can get. For example, the radius of curvature R may be 15 mm or more and the length b1 may be 10 mm or more.

[Modification 1-3]
FIG. 6 shows a modification of the cross-sectional shape shown in FIG. Of the curved portions 100 , 101 , 102 and 103 , the curved portion 100 having the largest radius of curvature is defined as the reference curved portion 10 . The longer planar portion 110 of the planar portions 110 and 113 that are continuous with both ends in the longitudinal direction of the reference curved portion 10 is referred to as the reference planar portion 11 . The angle θ formed by the first straight line L1 and the second straight line L2 with the reference curved portion 10 interposed therebetween is 100° to 110°. If the curvature radius R of the reference curved portion 10 satisfies the formula (1) and the length b1 of the reference flat portion 11 satisfies the formula (2), the same effect as the example shown in FIG. 1 can be obtained. can get. For example, the radius of curvature R may be 15 mm or more and the length b1 may be 10 mm or more.

<Second embodiment>
The vehicle body member 1 may be formed by joining a plurality of members molded into a predetermined shape into one by welding or the like. FIG. 7 shows an example of an axis-perpendicular cross-section of the vehicle body member 1 thus formed. This cross-section may be a closed cross-section. The vehicle body member 1 is formed in a tubular shape by joining a first member 1A and a second member 1B by welding. A cross section of the first member 1</b>A perpendicular to the axis has two curved portions 100 and 101 and three flat portions 110 , 111 and 112 . The flat portion 112 functions as a joining flange. The curved portion 101 may be a relatively small curved portion that normally occurs when the flat portion 112 is bent to form the flat portion 111 . A cross section of the second member 1B perpendicular to the axis has two curved portions 102 and 103 and three flat portions 113, 114 and 115. As shown in FIG. The flat portion 115 functions as a joining flange. Bend 103 may be a relatively small bend that would normally occur when flat portion 115 is bent to form flat portion 114 . The flat portion 112 of the first member 1A is joined to the longitudinal end portion of the flat portion 113 of the second member 1B via the welding portion 131 . A longitudinal end portion of the flat portion 110 of the first member 1A is joined to the flat portion 115 of the second member 1B via a weld portion 132 . The curved portions 101 and 103 are convex inside the vehicle body member 1 . Of the curved portions 100 , 101 , 102 and 103 , the curved portion 100 having the largest radius of curvature is defined as the reference curved portion 10 . The longer planar portion 110 of the planar portions 110 and 111 that are continuous with both ends in the longitudinal direction of the reference curved portion 10 is referred to as the reference planar portion 11 .

If the curvature radius R of the reference curved portion 10 satisfies the above formula (1) and the length b1 of the reference plane portion 11 satisfies the above formula (2), the same effects as in the first embodiment are obtained. effect is obtained. For example, the radius of curvature R may be 15 mm or more and the length b1 may be 10 mm or more. Note that the length b1 of the plane portion 110 as the reference plane portion 11 is the length from the connection portion with the bending portion 100 to the welded portion 132, and the length of the free end on the tip side of the welded portion 132 is Not included.

[Modification 2-1]
FIG. 8 shows a modification of the cross-sectional shape shown in FIG. A cross section of the first member 1A perpendicular to the axis has four curved portions 100, 101, 102, 103 and five flat portions 110, 111, 112, 114, 115. As shown in FIG. Flat portions 112 and 114 function as joining flanges. Bend portions 101 and 102 may be relatively small bends that would normally occur when flat portions 112 and 114 are bent to form flat portions 111 and 115, respectively. The second member 1B has a flat plate shape, and has one plane portion 113 in its cross section perpendicular to the axis. The flat portions 112 and 114 of the first member 1A are joined to the longitudinal ends of the flat portion 113 of the second member 1B via welding portions 131 and 132, respectively. The curvature radii of the curved portions 101 and 102 are the same, and the curvature radius of the curved portion 100 is larger than the curvature radius of the curved portion 101 . Since the curved portions 100 and 103 have the same radius of curvature, the curved portion 100 may be used as the reference curved portion 10, for example. The longer planar portion 110 of the planar portions 110 and 111 that are continuous with both ends in the longitudinal direction of the reference curved portion 10 is referred to as the reference planar portion 11 . If the curvature radius R of the reference curved portion 10 satisfies the formula (1) and the length b1 of the reference flat portion 11 satisfies the formula (2), the same effect as the example shown in FIG. 7 can be obtained. can get. For example, the radius of curvature R may be 15 mm or more and the length b1 may be 10 mm or more.

[Modification 2-2]
FIG. 9 shows a modification of the cross-sectional shape shown in FIG. A cross section of the first member 1A perpendicular to the axis has four curved portions 100, 101, 102, and 106 and five flat portions 110, 111, 112, 117, and 118. As shown in FIG. The flat portions 112 and 117 function as joining flanges. Bend portions 102 and 106 may be relatively small bends that would normally occur when flat portions 112 and 117 are bent relative to flat portions 111 and 118, respectively. A cross section of the second member 1B perpendicular to the axis has three curved portions 103, 104, 105 and four flat portions 113, 114, 115, 116. As shown in FIG. The plane portions 113 and 116 function as joining flanges. Bend portions 103 and 105 may be relatively small bends that would normally occur when flat portions 113 and 116 are bent relative to flat portions 114 and 115, respectively. The flat portions 112 and 117 of the first member 1A are joined to the flat portions 113 and 116 of the second member 1B via welding portions 131 and 132, respectively. The curved portion 100 having the largest curvature radius among the curved portions 100 to 106 is defined as the reference curved portion 10 . The longer planar portion 110 of the planar portions 110 and 118 that are continuous with both ends in the longitudinal direction of the reference curved portion 10 is referred to as the reference planar portion 11 . If the curvature radius R of the reference curved portion 10 satisfies the formula (1) and the length b1 of the reference flat portion 11 satisfies the formula (2), the same effect as the example shown in FIG. 7 can be obtained. can get. For example, the radius of curvature R may be 15 mm or more and the length b1 may be 10 mm or more.

[Modification 2-3]
FIG. 10 shows a modification of the cross-sectional shape shown in FIG. A cross section of the first member 1A perpendicular to the axis has four curved portions 100, 101, 106, 107 and five flat portions 110, 111, 112, 118, 119. As shown in FIG. Flat portions 112 and 118 function as joining flanges. Bend portions 101 and 106 may be relatively small bends that would normally occur when flat portions 112 and 118 are bent to form flat portions 111 and 119, respectively. A cross section of the second member 1B perpendicular to the axis has four curved portions 102, 103, 104, 105 and five flat portions 113, 114, 115, 116, 117. As shown in FIG. The flat portions 113 and 117 function as joining flanges. Bend portions 102 and 105 may be relatively small bends that would normally occur when flat portions 113 and 117 are folded to form flat portions 114 and 116, respectively. The flat portions 112, 118 of the first member 1A are joined to the flat portions 113, 117 of the second member 1B via welding portions 131, 132, respectively. The curved portion 100 having the largest radius of curvature among the curved portions 100 to 107 is defined as the reference curved portion 10 . The longer planar portion 110 of the planar portions 110 and 111 that are continuous with both ends in the longitudinal direction of the reference curved portion 10 is referred to as the reference planar portion 11 . If the curvature radius R of the reference curved portion 10 satisfies the formula (1) and the length b1 of the reference flat portion 11 satisfies the formula (2), the same effect as the example shown in FIG. 7 can be obtained. can get. For example, the radius of curvature R may be 15 mm or more and the length b1 may be 10 mm or more.

[Modification 2-4]
FIG. 11 shows a modification of the cross-sectional shape shown in FIG. The cross section of the vehicle body member 1 in the direction perpendicular to the axis is a substantially hat-shaped closed cross section. The first member 1A has eight curved portions 100, 101, 102, 103, 104, 105, 106, and 107 and seven flat portions 110, 111, 112, 113, 115, 116, and 117. have The flat portions 113 and 115 function as joining flanges. Bend portions 104 and 105 may be relatively small bends that would normally occur when flat portions 113 and 115 are bent relative to flat portions 112 and 116, respectively. The curved portion 100 and the curved portion 107 are continuous with each other without passing through the plane portion. The curved portion 101 and the curved portion 102 are continuous with each other without passing through the plane portion. The curved portions 100 , 101 , 102 , 107 and the flat portion 110 form a concave portion 12 projecting inwardly of the vehicle body member 1 from the flat portions 111 , 117 . The recess 12 has a groove shape extending along the longitudinal direction (axial direction) of the vehicle body member 1 . The second member 1B has a flat plate shape, and has one plane portion 114 in its cross section perpendicular to the axis. The flat portions 113 and 115 of the first member 1A are joined to the longitudinal ends of the flat portion 113 of the second member 1B via welding portions 131 and 132, respectively. The curved portions 100 and 101 are convex inside the vehicle body member 1 . The radius of curvature of curved portions 100 and 101 is greater than the radius of curvature of the other curved portions 102-107. Since the curved portions 100 and 101 have the same radius of curvature, the curved portion 100 may be used as the reference curved portion 10, for example. Since the plane portion continues to only one of the longitudinal ends of the reference curved portion 10 , this plane portion 110 is referred to as the reference plane portion 11 .

If the curvature radius R of the reference curved portion 10 satisfies the formula (1) and the length b1 of the reference flat portion 11 satisfies the formula (2), the same effect as the example shown in FIG. 7 can be obtained. can get. For example, the radius of curvature R may be 15 mm or more and the length b1 may be 10 mm or more. In this modified example, since the flat portion of the first member 1A is divided into three, the length of each flat portion 110, 111, 117 in the section perpendicular to the axis is shortened, and the right side of the above equation (2) is It tends to fall below the specified upper limit. Thereby, elastic buckling is suppressed in each flat portion. In addition, since the first member 1A has the concave portion 12, the resistance of the vehicle body member 1 against bending moment is improved, and the impact absorption characteristics are also improved.

[Examples of application of car body members]
The preferred embodiments of the present invention have been described in detail above. From here, an application example of the vehicle body member 1 according to the embodiment will be described with reference to FIG. 12 . FIG. 12 is a diagram showing an automobile frame 2 as an example to which the vehicle body member 1 is applied. The vehicle body member 1 can constitute the automobile skeleton 2 as a cabin skeleton or an impact-absorbing skeleton.

Application examples of the vehicle body member 1 as a cabin frame include a roof centering force 201, a roof side rail 203, a B pillar 207, a side sill 209, a tunnel 211, an A pillar lower 213, an A pillar upper 215, a kick reinforcement 227, and a floor cross member. 229, under reinforcement 231, front header 233, and the like. Further, application examples of the vehicle body member 1 as a shock absorbing skeleton include the rear side member 205, the apron upper member 217, the bumper reinforcement 219, the crash box 221, the front side member 223, and the like. In addition to the above, the vehicle body member 1 may be applied to a door impact beam or the like as a reinforcing member provided inside the door of an automobile. In short, the vehicle body member 1 of the present embodiment can be applied to any part where a compressive force can act in the axial direction.

When the vehicle body member 1 is used as a cabin frame or a shock absorbing frame in this way, the vehicle body member 1 has a high axial compressive strength, so that deformation at the time of collision can be reduced. In addition, deformability is improved, and the inside of the skeleton can be protected.

Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also naturally belong to the technical scope of the present invention.

For example, there may be at least one curved portion in the cross section of the vehicle body member in the direction perpendicular to the axis, and the number of curved portions may be one. In addition, it suffices that there is at least one plane portion in the cross-section in the direction perpendicular to the axis of the vehicle body member, and the number of plane portions may be one. The cross section of the vehicle body member in the direction perpendicular to the axis may not be a closed cross section, and may be an open cross section. For example, in the modifications shown in FIGS. 8 to 11, the second member 1B may be omitted and only the first member 1A may be used as the vehicle body member. In these cases as well, the longitudinal ends of the reference flat portion can be regarded as being simply supported in the cross section in the direction perpendicular to the axis.

1 vehicle body member 10 reference curved portion 11 reference plane portion L1 first straight line L2 second straight line

Claims (4)

Tunnel, kick reinforcement, floor cross member, or under reinforcement body member,
formed of a steel plate having a thickness of 1.6 mm or less,
The shape of the cross section perpendicular to the axis is
having at least one outwardly or inwardly convex curved portion and at least one planar portion;
one curved portion having the largest radius of curvature as a reference curved portion;
If the plane portion is continuous with only one end of the longitudinal direction ends of the reference curved portion, the plane portion is continuous, and if the plane portion is continuous with both ends, the longer plane portion is selected. as the reference plane,
a straight line extending in a tangential direction of the reference curved portion from one end of the reference curved portion in the longitudinal direction at which the reference flat portion is not continuous is defined as a first straight line;
An extension line of the reference plane portion is defined as a second straight line,
Let b0 be the length between the intersection point of the first straight line and the second straight line and the end of the reference flat portion that is not continuous with the reference curved portion among the longitudinal ends of the reference flat portion;
The length of the reference plane portion is b1,
When the radius of curvature of the reference curved portion is R,
satisfying the following formulas (1) and (2),
The steel plate has a tensile strength of 1180 MPa or more,
The R is 15 mm or more,
A body member that is either a tunnel, kick reinforce, floor cross member or under reinforce .
However, the plate thickness of the steel plate forming the reference flat portion is t, Young's modulus is E, Poisson's ratio is ν, and yield stress is _σy .

The vehicle body member according to claim 1 , wherein said b1 is 10 mm or more. 3. The vehicle body member according to claim 1, wherein an angle formed by said first straight line and said second straight line with said reference curved portion interposed therebetween is 80[deg.] or more and 150[deg.] or less . A vehicle body member according to any one of claims 1 to 3 , wherein said transverse section is a closed section.

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