Patent Description:
In recent years, application of high-tensile steel sheets to automobile components has been expanding for the purposes of improving collision safety performance of automobiles and reducing the weight for an automobile body. By applying a high-tensile steel sheet, it is possible to obtain components having more excellent collision safety performance, or to achieve both collision safety performance and weight reduction by thinning.

However, when a sheet thickness of a material becomes thin, not only does stiffness of the steel sheet before processing decrease, but stiffness of the components after processing also decreases. Therefore, if a steel sheet having high strength and a thin sheet thickness is simply used, a sufficient effect of increasing the strength of collision safety performance may not be obtained.

Collision safety performance of automobile body components includes bending-crushing characteristics of a side sill or a B pillar in a side collision, a bumper in a front collision, or the like. It is desired to increase three-point bending characteristics in a local buckling mode as the bending-crushing characteristics of these components and to exhibit higher collision safety performance even when a material having a thin sheet thickness is used.

A collision-resistant reinforcing material for vehicles which has excellent buckling resistance and is designed to provide a concave bead extending in a longitudinal direction of a main body portion at a center of the main body portion in a width direction is disclosed in Patent Document <NUM>.

A metal absorber for vehicles which has concave or convex beads substantially parallel to a front-rear direction of a vehicle on one or both of an upper web and a lower web is disclosed in Patent Document <NUM>. Patent Document <NUM> relates to a bumper beam having a hat-shaped profile with a cover, wherein the cover is welded to the sides of the hat-shaped profile, inside the hat-shaped profile. Patent Document <NUM> relates to a vehicle body structure having pillars to which door hinges are attached.

However, in the techniques of Patent Documents <NUM> and <NUM>, higher three-point bending characteristics in the local buckling mode of bending-crushing components which is required could not be sufficiently exhibited.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a structural member capable of exhibiting excellent collision safety performance by improving a load capacity at an initial stage of a stroke of a deformation in a local buckling mode.

In the following description, although numerous features may be designated as optional, it is nevertheless acknowledged that all features comprised in the independent claim are not to be read as optional. Specific aspects of the present invention are as follows.

According to a first aspect of the present invention, there is provided a structural member for an automobile body, including: a hat channel member that has a top sheet portion extending in a longitudinal direction, a pair of side wall portions extending via first corner portions formed at both end portions of the top sheet portion in a width direction, and a pair of flange portions extending via second corner portions formed at end portions of the pair of side wall portions on sides opposite to the first corner portions; and a joining member that has a pair of joining portions joined to the pair of flange portions of the hat channel member, and a top sheet facing portion facing the top sheet portion of the hat channel member, wherein a first bead extending in the longitudinal direction is formed on the top sheet facing portion, and wherein two or more second beads extending in a direction intersecting the longitudinal direction are formed on the pair of side wall portions, wherein two or more of the first beads are formed in parallel in the width direction, wherein the first bead bulges inward from the top sheet facing portion in a cross section perpendicular to the longitudinal direction, and wherein the first bead is formed such that a center of the first bead in the width direction is positioned in a region from an inner end portion of the joining portion of the joining member to a point having a separation distance of <NUM>/<NUM> of a width of the top sheet facing portion in the width direction in a cross section perpendicular to the longitudinal direction, or wherein the first bead is formed such that a boundary point between the first bead and the joining member is positioned in a region from an inner end portion of the joining portion of the joining member to a point having a separation distance of <NUM> in a cross section perpendicular to the longitudinal direction.

The second bead may extend from the second corner portion.

The second bead may extend to the first corner portion.

A width of the first bead may be <NUM> to <NUM>, and a depth of the first bead may be <NUM> to <NUM>.

An aspect ratio calculated as a depth/a width of the first bead may be <NUM> to <NUM>.

A width of the second bead may be <NUM> to <NUM>, and a depth of the second bead may be <NUM> to <NUM>.

An aspect ratio calculated as a depth/a width of the second bead may be <NUM> to <NUM>.

The top sheet portion of the hat channel member may be formed of a steel sheet having a sheet thickness of <NUM> or less.

The top sheet portion of the hat channel member may be formed of a steel sheet having a tensile strength of <NUM> MPa or more.

The hat channel member may be a quenched member.

The joining member may be a steel sheet having a sheet thickness of <NUM> or less.

The joining member may be a steel sheet having a tensile strength of <NUM> MPa or more.

The joining member may be a quenched member.

According to the present invention, it is possible to increase deformation resistance against each of a stress in a longitudinal direction and a stress in a height direction generated in components with respect to three-point bending characteristics in a local buckling mode of bending-crushing components and to obtain high collision safety performance even when a material having a thin sheet thickness is used.

Bending-crushing characteristics of an automobile component are roughly divided into three-point bending characteristics in a case where impact of a collision is directly applied to a crushing portion of the component to deform the crushing portion and moment bending characteristics in a case where impact of a collision is indirectly applied to a crushing portion of the component to deform the crushing portion.

Of these, the three-point bending characteristics are classified into three-point bending characteristics in a local budding mode and three-point bending characteristics in a wall buckling mode.

The three-point bending characteristics in a local buckling mode and the three-point bending characteristics in a wall buckling mode are often evaluated on the basis of three-point bending characteristics obtained by performing a three-point bending test in which an impactor directly collides with the component as shown in <FIG>.

In the three-point bending characteristics in a local buckling mode, bending deformation at a load-applying position of the impactor under a condition that a distance between fulcrums supporting a load is long in the three-point bending test is a main constituent.

In the three-point bending characteristics in a wall buckling mode, deformation in which a side wall is crushed in a height direction of the component with a load applying-position of the impactor as a center under a condition that a distance between fulcrums supporting a load is short in the three-point bending test is a main constituent.

Further, as shown in <FIG>, the moment bending characteristics are often evaluated on the basis of moment bending characteristics obtained by performing a moment bending test in which the impactor or the like does not come into contact with the crushing portion of the component.

The present inventor examined a shape of the component for enhancing collision safety performance with respect to the deformation in the local buckling mode as shown in <FIG> and obtained the following findings.

Hereinafter, the present invention completed on the basis of the above findings will be described in detail on the basis of embodiments. In the present specification and the drawings, elements having substantially the same functional configuration are designated by the same reference symbols, and duplicate descriptions thereof will be omitted.

In the following description, an axial direction of a structural member, that is, a direction in which an axis extends, is referred to as a longitudinal direction Z.

Further, a direction parallel to a top sheet portion on a plane perpendicular to the longitudinal direction Z is referred to as a width direction X, and a direction perpendicular to the longitudinal direction Z and the width direction X is referred to as a height direction Y.

A direction away from the axis of the structural member is referred to as an outward direction, and a direction opposite to the outward direction is referred to as an inward direction.

Hereinafter, a structural member <NUM> of an automobile body according to a first embodiment of the present invention (hereinafter referred to as a structural member <NUM>) will be described.

First, a schematic configuration of the structural member <NUM> will be described with reference to <FIG>.

As shown in <FIG>, the structural member <NUM> is a member having a closed cross-section structure constituted by a hat channel member <NUM> and a joining member <NUM>. Application examples of the structural member <NUM> include a bumper reinforcement and the like.

The structural member <NUM> according to the present embodiment is a component which is assumed to be installed in an automobile in a posture in which the hat channel member <NUM> faces the inside of the automobile and the joining member <NUM> faces the outside of the automobile.

<FIG> is a cross-sectional view along line A-A' of <FIG>. As shown in <FIG>, the hat channel member <NUM> has a top sheet portion <NUM> extending in the longitudinal direction Z, a pair of side wall portions <NUM> and <NUM> extending via first corner portions <NUM> and <NUM> formed at both ends of the top sheet portion <NUM> in the width direction X, and a pair of flange portions <NUM> and <NUM> extending via second corner portions <NUM> and <NUM> formed at end portions of the pair of side wall portions <NUM> and <NUM> on sides opposite to the first corner portions <NUM> and <NUM>.

The hat channel member <NUM> may be a member made of a resin sheet, a carbon fiber reinforced plastic (CFRP) sheet, or a metal sheet (an aluminum sheet, an aluminum alloy sheet, a stainless sheet, a titanium sheet, a steel sheet, or the like).

The hat channel member <NUM> can be easily formed by, for example, cold press-forming or warm press-forming of a sheet material.

Further, the hat channel member <NUM> may be formed by hot stamping in which a steel sheet is heated to a high temperature in an austenite region and then is press-formed by a die, and at the same time, quenching treatment is performed in the die. Therefore, the hat channel member <NUM> may be a quenched member.

The top sheet portion <NUM> corresponds to a side opposite to a portion in direct contact with the impactor in the three-point bending test in the local buckling mode shown in <FIG>.

The structural member <NUM> according to the present embodiment is installed in an automobile in a posture in which the hat channel member <NUM> faces the inside of the automobile. Therefore, when an impact load from the outside of the automobile is input to the joining member <NUM> and bending deformation occurs in the structural member <NUM>, a tensile stress in the longitudinal direction Z is generated in the top sheet portion <NUM>. Therefore, since the top sheet portion <NUM> can increase the deformation resistance against the tensile stress in the longitudinal direction Z, it is possible to exhibit high collision safety performance.

From the viewpoint of weight reduction, the top sheet portion <NUM> is preferably formed of a steel sheet having a sheet thickness of <NUM> or less and is more preferably formed of a steel sheet having a sheet thickness of <NUM> or less. A lower limit of the sheet thickness of the top sheet portion <NUM> is not particularly limited and may be <NUM> or more.

Further, from the viewpoint of the collision safety performance, the top sheet portion <NUM> is preferably formed of a steel sheet having a tensile strength of <NUM> MPa or more and is more preferably formed of a steel sheet having a tensile strength of <NUM> MPa or more.

A width of the top sheet portion <NUM> may be appropriately designed in consideration of a width W of the top sheet facing portion <NUM> of the joining member <NUM>, which will be described later.

A pair of side wall portions <NUM> and <NUM> extend via the first corner portions <NUM> and <NUM> formed at both end portions of the top sheet portion <NUM> in the width direction X. The first corner portions <NUM> and <NUM> have an R portion having a radius of curvature of <NUM> to <NUM>, for example.

Since the structural member <NUM> according to the present embodiment is installed in the automobile in a posture in which the hat channel member <NUM> faces the inside of the automobile, when an impact load from the outside of the automobile is input to the joining member <NUM> and bending deformation occurs in the structural member <NUM>, a compressive stress in a direction intersecting the longitudinal direction Z, that is, a compressive stress along the side wall portion <NUM> in a cross section perpendicular to the longitudinal direction Z of the structural member <NUM>, is generated in the pair of side wall portions <NUM> and <NUM>.

A second bead <NUM> formed on the side wall portion <NUM> will be described later.

A sheet thickness and a tensile strength of the side wall portion <NUM> may be the same as the sheet thickness and the tensile strength of the top sheet portion <NUM>.

A height H of the side wall portion <NUM> may be <NUM> or more and <NUM> or less. As shown in <FIG>, the height H of the side wall portion <NUM> is a separation distance in the height direction Y between a boundary point of the side wall portion <NUM> and the first corner portion <NUM> and a boundary point of the side wall portion <NUM> and the second corner portion <NUM> in the cross section perpendicular to the longitudinal direction Z of the structural member <NUM>. The second corner portions <NUM> and <NUM> have an R portion having a radius of curvature of <NUM> to <NUM>, for example.

As shown in <FIG>, the second corner portions <NUM> and <NUM> are formed at the end portions of the pair of side wall portions <NUM> and <NUM> opposite to the first corner portions <NUM> and <NUM>. The pair of flange portions <NUM> and <NUM> are formed to extend outward from the second corner portions <NUM> and <NUM>.

Spot welded portions <NUM> for joining the flange portion <NUM> to the joining member <NUM> are formed on the flange portion <NUM> at a predetermined pitch in the longitudinal direction Z. Spot welding is an example of means for joining, and laser welding or brazing is also possible.

Hereinafter, the joining member <NUM> will be described.

The joining member <NUM> corresponds to a portion in direct contact with the impactor in the three-point bending test in the local buckling mode shown in <FIG>.

The joining member <NUM> is a member that is joined to the hat channel member <NUM>. Since the structural member <NUM> according to the present embodiment is installed in the automobile in a posture in which the joining member <NUM> faces the outside of the automobile, when an impact load from the outside of the automobile is input to the joining member <NUM> and bending deformation occurs in the structural member <NUM>, a compressive stress in the longitudinal direction Z is generated in the joining member <NUM>.

Therefore, since the joining member <NUM> can increase the deformation resistance against the compressive stress in the longitudinal direction Z, it is possible to exhibit high collision safety performance.

Further, by joining the joining member <NUM> to the hat channel member <NUM>, it is possible to prevent the side wall portion <NUM> from opening in the width direction X when the bending deformation occurs in the structural member <NUM>. Therefore, it is possible to prevent a decrease in the three-point bending characteristics and to exhibit high collision safety performance.

As shown in <FIG> and <FIG>, in the structural member <NUM> according to the present embodiment, one sheet material on which two first beads <NUM> and <NUM>, which will be described later, are formed is used as the joining member <NUM>.

The joining member <NUM> may be a member made of a resin sheet, a carbon fiber reinforced plastic (CFRP) sheet, or a metal sheet (an aluminum sheet, an aluminum alloy sheet, a stainless sheet, a titanium sheet, a steel sheet, or the like).

From the viewpoint of weight reduction, the joining member <NUM> is preferably formed of a steel sheet having a sheet thickness of <NUM> or less and is more preferably formed of a steel sheet having a sheet thickness of <NUM> or less.

A lower limit of the sheet thickness of the joining member <NUM> is not particularly limited and may be <NUM> or more.

Further, from the viewpoint of the collision safety performance, the joining member <NUM> is preferably formed of a steel sheet having a tensile strength of <NUM> MPa or more and is more preferably formed of a steel sheet having a tensile strength of <NUM> MPa or more.

The joining member <NUM> may be a quenched member.

As shown in <FIG>, the joining member <NUM> has a pair of joining portions <NUM> and <NUM> provided at both ends in the width direction X and a top sheet facing portion <NUM> provided at a center in the width direction X.

The pair of joining portions <NUM> and <NUM> are portions with which the pair of flange portions <NUM> and <NUM> of the hat channel member <NUM> to be joined by spot welding or the like come into surface contact.

The top sheet facing portion <NUM> is a portion of the joining member <NUM> excluding the joining portion <NUM> and is a portion facing the top sheet portion <NUM> of the hat channel member <NUM>. The top sheet portion <NUM> does not have a structure that supports the top sheet facing portion <NUM> from the inside. That is, the top sheet portion <NUM> is not in contact with an inner surface of the top sheet facing portion <NUM>. Since the length of the perimeter of a cross section surrounded by a closed cross section of the structural member <NUM> relative to area can be reduced, the three-point bending characteristics obtained relative to the weight of the member (for example, the maximum load) can be efficiently increased. That is, weight reduction can be realized.

In the structural member <NUM> according to the present embodiment, since the joining member <NUM> is constituted by a single sheet-shaped steel sheet, the joining portion <NUM> and the top sheet facing portion <NUM> are flush with each other and adjacent to each other.

The first bead <NUM> formed on the top sheet facing portion <NUM> will be described later.

A width W of the top sheet facing portion <NUM> may be <NUM> or more and <NUM> or less. The width W of the top sheet facing portion <NUM> is preferably larger than the width of the top sheet portion <NUM>. In this case, the pair of side wall portions <NUM> and <NUM> are inclined to expand outward from the first corner portions <NUM> and <NUM> to the second corner portions <NUM> and <NUM>. In a case where an impact load from the outside of the automobile is input to the joining member <NUM>, under a condition that the second bead <NUM> is disposed on the side wall portion <NUM>, the pair of side wall portions <NUM> and <NUM> are likely to collapse in a direction in which the pair of side wall portions <NUM> and <NUM> on sides of the first corner portions <NUM> and <NUM> approach each other, but the top sheet portion <NUM> can support the pair of side wall portions <NUM> and <NUM> via the first corner portions <NUM> and <NUM>. Therefore, an effect that the cross section perpendicular to the longitudinal direction Z of the hat channel member <NUM> is less likely to be crushed can be obtained. Further, in a case where the hat channel member <NUM> is press-formed, a negative angle (undercut) occurring when the height direction Y is set as a press direction can be eliminated, and thus an effect that a forming process is facilitated can be obtained. Further, since the structural member <NUM> according to the present embodiment is constituted by the hat channel member <NUM> and the joining member <NUM>, an effect that the length of the perimeter of a cross-section surrounded by a closed cross section relative to area can be reduced and the three-point bending characteristics obtained relative to the weight of the member (for example, the maximum load) can be efficiently increased can be obtained.

Hereinafter, the first bead and the second bead will be described.

Two first beads <NUM> and <NUM> in the longitudinal direction Z are formed on the top sheet facing portion <NUM> in parallel.

As shown in <FIG>, the first bead <NUM> is formed to bulge inward from the top sheet facing portion <NUM> at a central portion of the top sheet facing portion <NUM> in the width direction X.

The first bead <NUM> may have an R portion having a predetermined radius of curvature at an end portion on a side of the top sheet facing portion <NUM>. In that case, the first bead <NUM> is connected to the top sheet facing portion <NUM> via the R portion of the first bead <NUM>.

By providing such a first bead <NUM>, it is possible to increase the deformation resistance against the compressive stress in the longitudinal direction Z generated in the joining member <NUM>. As a result, when the structural member <NUM> is subjected to bending deformation, the occurrence of early buckling deformation in the joining member <NUM> is curbed and the maximum load is increased.

The first bead <NUM> can be formed by press-forming of a sheet material.

As shown in <FIG>, the first bead <NUM> is formed by a pair of bead side walls <NUM> and <NUM> and a bead bottom sheet <NUM>.

The pair of bead side walls <NUM> and <NUM> bend from the top sheet facing portion <NUM> and extend inward.

The bead bottom sheet <NUM> extends to connect end portions of the pair of bead side walls <NUM> and <NUM> opposite to the top sheet facing portion <NUM>.

As shown in <FIG>, the first bead <NUM> has a predetermined depth d1 and a predetermined width w1.

The depth d1 of the first bead <NUM> is a separation distance in the height direction Y from an outer surface of the top sheet facing portion <NUM> to an outer surface of the bead bottom sheet <NUM> in the first bead <NUM>. In a case where the first bead <NUM> has a shape in which the depth changes in the longitudinal direction Z, the maximum value of the separation distance in the height direction Y from the top sheet facing portion <NUM> to the bead bottom sheet <NUM> is defined as the depth d1.

As the depth d1 of the first bead <NUM> becomes larger, it is possible to increase the deformation resistance against the compressive stress in the longitudinal direction Z generated in the joint member <NUM>, and the early buckling deformation in the joining member <NUM> is curbed and the maximum load is increased. Therefore, the depth d1 of the first bead <NUM> is preferably <NUM> or more and is more preferably <NUM> or more.

On the other hand, if the depth d1 of the first bead <NUM> is too large and the width w1 of the first bead <NUM> is relatively small, the forming process of the first bead <NUM> may be difficult. Therefore, the depth d1 of the first bead <NUM> is preferably <NUM> or less and is more preferably <NUM> or less.

The width w1 of the first bead <NUM> is a separation distance between an intersection point of a virtual straight line extending on one bead side wall <NUM> of the first bead <NUM> and a virtual straight line extending on the top sheet facing portion <NUM> and an intersection point of a virtual straight line extending on the other bead side wall <NUM> of the first bead <NUM> and the virtual straight line extending on the top sheet facing portion <NUM> in the outer surface of the top sheet facing portion <NUM> having a cross section perpendicular to the longitudinal direction Z.

In a case where the first bead <NUM> has a shape in which the width changes in the longitudinal direction Z, a separation distance in a cross section where the separation distance is maximum is defined as the width w1.

As the width w1 of the first bead <NUM> becomes smaller, it is possible to increase the deformation resistance against the compressive stress in the longitudinal direction Z generated in the joint member <NUM>, and the early buckling deformation in the joining member <NUM> is curbed and the maximum load is increased. Therefore, the width w1 of the first bead <NUM> is preferably <NUM> or less and is more preferably <NUM> or less.

On the other hand, if the width w1 of the first bead <NUM> is too small and the depth d1 of the first bead <NUM> is relatively large, the forming process of the first bead <NUM> may be difficult. Therefore, the width w1 of the first bead <NUM> is preferably <NUM> or more and is more preferably <NUM> or more.

The first bead <NUM> does not necessarily have to be formed over the entire length of the top sheet facing portion <NUM> in the longitudinal direction Z and may be formed over a part of the entire length of the top sheet facing portion <NUM>. As a position where the first bead <NUM> is formed, a position where the structural member <NUM> has to be most strengthened in the bending-crushing characteristics, for example, a position where the impactor comes into contact with the structural member <NUM> (a position where a collision load is input), and the vicinity thereof may be selected. Further, the first beads <NUM> may be formed at a plurality of positions in the longitudinal direction Z.

As described above, the depth d1 and the width w1 of the first bead <NUM> influence the deformation resistance against the compressive stress in the longitudinal direction Z generated in the joining member <NUM>. In a case where an aspect ratio A1 obtained by the depth d1 with respect to the width w1 (the depth d1/the width w1) of the first bead <NUM> is <NUM> or more and <NUM> or less, this is preferable because an effect of increasing the deformation resistance against the compressive stress in the longitudinal direction Z generated in the joining member <NUM> can be more reliably exhibited. It is more preferable that the aspect ratio A1 be <NUM> or more and <NUM> or less.

A plurality of second beads <NUM> in a direction intersecting the longitudinal direction Z are formed on the pair of side wall portions <NUM> and <NUM> in parallel.

<FIG> is a schematic bottom view of the structural member <NUM> according to the present embodiment, and <FIG> is an enlarged view of portion B of <FIG>.

As shown in <FIG>, the second bead <NUM> is formed to bulge inward from the side wall portion <NUM>.

The second bead <NUM> may have an R portion having a predetermined radius of curvature at an end portion on a side of the side wall portion <NUM>. In that case, the second bead <NUM> is connected to the side wall portion <NUM> via the R portion of the second bead <NUM>.

By providing such a second bead <NUM>, it is possible to increase the deformation resistance against the compressive stress in a direction intersecting the longitudinal direction Z generated in the side wall portion <NUM>. As a result, early buckling deformation in the side wall portion <NUM> is curbed and the maximum load is increased.

The second bead <NUM> is preferably formed on each side wall portion <NUM> of the pair of side wall portions <NUM> and <NUM>. As a result, it is possible to further increase the deformation resistance against the compressive stress in a direction intersecting the longitudinal direction Z generated in the side wall portion <NUM> as compared with the case where the second bead <NUM> is formed only on one side wall portion <NUM>.

In the structural member <NUM> according to the present embodiment, the second bead <NUM> is formed to extend from the second corner portion <NUM> to the first corner portion <NUM>.

Since the second bead <NUM> is formed to extend from the second corner portion <NUM>, the second bead <NUM> also contributes to the deformation resistance of the second corner portion <NUM> in the height direction Y, and the second corner portion <NUM> is less likely to be crushed. This is preferable because the second corner portion <NUM> and the side wall portion <NUM> are less likely to be crushed, and thus the decrease in the bending rigidity in the height direction Y of the cross section intersecting the longitudinal direction Z due to the decrease in the height of the structural member <NUM> can be curbed, and the decrease of the three-point bending characteristics in the local buckling mode can be prevented.

Further, since the second bead <NUM> is formed to extend from the second corner portion <NUM> to the first corner portion <NUM>, the second bead <NUM> also contributes to the deformation resistance of the first corner portion <NUM> in the height direction Y, and the first corner portion <NUM> is also less likely to be crushed. Therefore, this is preferable because the first corner portion <NUM>, the side wall portion <NUM>, and the second corner portion <NUM> are less likely to be crushed, and thus the decrease in the bending rigidity in the height direction Y of the cross section intersecting the longitudinal direction Z due to the decrease in the height of the structural member <NUM> can be further curbed, and the decrease in the three-point bending characteristics in the local buckling mode can be further prevented. In a case where the second bead <NUM> is formed to extend to the first corner portion <NUM> in this way, a step caused by a portion of a bead bottom sheet <NUM> of the second bead <NUM>, which will be described later, and a portion of the side wall portion <NUM> on which the second bead <NUM> is not formed is formed on the first corner portion <NUM> in the longitudinal direction Z.

The second bead <NUM> may be simultaneously formed with the same die when the top sheet portion <NUM>, the side wall portion <NUM>, and the flange portion <NUM> are press-formed, or may be formed with another die or tool before the top sheet portion <NUM>, the side wall portion <NUM>, and the flange portion <NUM> are press-formed.

As shown in <FIG>, the second bead <NUM> is formed by a pair of bead side walls <NUM> and <NUM> and a bead bottom sheet <NUM>.

The pair of bead side walls <NUM> and <NUM> bend from the side wall portion <NUM> and extend inward.

The bead bottom sheet <NUM> extends to connect end portions of the pair of bead side walls <NUM> and <NUM> opposite to the side wall portion <NUM>.

As shown in <FIG>, the second bead <NUM> has a predetermined depth d2 and a predetermined width w2.

The depth d2 of the second bead <NUM> is a separation distance in the width direction X from an outer surface of the side wall portion <NUM> to an outer surface of the bead bottom sheet <NUM> in the second bead <NUM>. In a case where the second bead <NUM> has a shape in which the depth changes in a direction intersecting the longitudinal direction Z, the maximum value of the separation distance in the width direction X from the side wall portion <NUM> to the bead bottom sheet <NUM> is defined as the depth d2.

As the depth d2 of the second bead <NUM> becomes larger, it is possible to further increase the deformation resistance against the compressive stress in a direction intersecting the longitudinal direction Z generated in the side wall portion <NUM>. Therefore, the depth d2 of the second bead <NUM> is preferably <NUM> or more and is more preferably <NUM> or more.

On the other hand, if the depth d2 of the second bead <NUM> is too large, the dimension of the structural member <NUM> in the width direction X becomes a locally small value, and the bending rigidity in the cross section intersecting the longitudinal direction Z becomes too small, the desired three-point bending characteristics may not be obtained. Further, as will be described later, in a configuration in which the first bead <NUM> is formed in the vicinity of the end portion of the top sheet facing portion <NUM> in the width direction X, if the depth d2 of the second bead <NUM> is too large, the first bead <NUM> may not be formed at a desired position. Further, if the depth d2 of the second bead <NUM> is too large and the width w2 of the second bead <NUM> is relatively small, the forming process of the second bead <NUM> may be difficult. Therefore, the depth d2 of the second bead <NUM> is preferably <NUM> or less and is more preferably <NUM> or less.

The plurality of second beads <NUM> are preferably formed with a distance between the beads of <NUM> or less in the longitudinal direction Z of the side wall portion <NUM> and are more preferably formed with a distance between the beads of <NUM> or less in the longitudinal direction Z of the side wall portion <NUM>. In this case, it is possible to further increase the deformation resistance against the compressive stress in a direction intersecting the longitudinal direction Z generated in the side wall portion <NUM>. As shown in <FIG>, the distance between the beads is a separation distance between one end portion of the second bead <NUM> and the other end portion of the adjacent second bead <NUM>.

The plurality of second beads <NUM> do not have to be formed over the entire length of the side wall portion <NUM> and only have to be formed over a part of the entire length of the side wall portion <NUM>. As a position where the plurality of second beads <NUM> are formed, a position where the structural member <NUM> is most strengthened in the bending-crushing characteristics, for example, a position where the impactor comes into contact with the structural member <NUM>, and the vicinity thereof may be selected.

Further, the plurality of second beads <NUM> do not have be formed side by side at the side wall portion <NUM> with an equal distance between the beads. For example, in a case where three second beads <NUM> are formed, the distances between the two beads may be different values.

Further, the plurality of second beads <NUM> do not necessarily have to be formed at the same position in the longitudinal direction Z in the pair of side wall portions <NUM> and <NUM>. For example, at the same position in the longitudinal direction Z as the second bead <NUM> formed on one side wall portion <NUM>, the second bead <NUM> may not be formed on the other side wall portion <NUM>.

The width w2 of the second bead <NUM> is a separation distance between an intersection point of a virtual straight line extending on one bead side wall <NUM> of the second bead <NUM> and a virtual straight line extending on the side wall portion <NUM> and an intersection point of a virtual straight line extending on the other bead side wall <NUM> of the second bead <NUM> and the virtual straight line extending on the side wall portion <NUM> in the outer surface of the side wall portion <NUM> having a cross section perpendicular to the height direction Y.

In a case where the second bead <NUM> has a shape in which the width changes in a direction intersecting the longitudinal direction Z, a separation distance in a cross section where the separation distance is maximum is defined as the width w2.

As the width w2 of the second bead <NUM> becomes smaller, it is possible to further increase the deformation resistance against the compressive stress in a direction intersecting the longitudinal direction Z generated in the side wall portion <NUM>. Therefore, the width w2 of the second bead <NUM> is preferably <NUM> or less and is more preferably <NUM> or less.

On the other hand, if the width w2 of the second bead <NUM> is too small and the depth d2 of the second bead <NUM> is relatively large, the forming process of the second bead <NUM> may be difficult. Therefore, the width w2 of the second bead <NUM> is preferably <NUM> or more and is more preferably <NUM> or more.

As described above, the depth d2 and the width w2 of the second bead <NUM> influence the deformation resistance against the compressive stress in a direction intersecting the longitudinal direction Z generated in the side wall portion <NUM>. In a case where an aspect ratio A2 obtained by the depth d2 with respect to the width w2 (the depth d2/the width w2) of the second bead <NUM> is <NUM> or more and <NUM> or less, this is preferable because an effect of increasing the deformation resistance against the compressive stress in a direction intersecting the longitudinal direction Z generated in the side wall portion <NUM> can be more reliably exhibited. It is more preferable that the aspect ratio A2 be <NUM> or more and <NUM> or less.

The structural member <NUM> according to the present embodiment described above has a perpendicular cross-section portion that forms the first beads <NUM> and <NUM> and the second bead <NUM> on at least one of the pair of side wall portions <NUM> and <NUM> in a cross section perpendicular to the longitudinal direction Z. According to the structural member <NUM> of the present embodiment, when an impact load from the outside of the automobile is input to the joining member <NUM> and bending deformation occurs in the structural member <NUM>, as shown in <FIG>, the deformation resistance against the compressive stress (A) in the longitudinal direction Z generated in the joining member <NUM>, the deformation resistance against the compressive stress (B) in a direction intersecting longitudinal direction Z generated in the side wall portion <NUM>, and the deformation resistance against the tensile stress (C) in the longitudinal direction Z generated in the top sheet portion <NUM> can be exhibited in a complex manner. As a result, the load capacity can be improved especially at the initial stage of the stroke, and the collision safety performance can be improved.

Since the deformation resistance decreases as the sheet material becomes thinner, the reduction in the deformation resistance due to thinning has been one of barriers to weight reduction with the use of a thinned high-strength material in the related art. That is, for example, even if the deformation resistance of the joining member <NUM> in the longitudinal direction Z is increased by increasing the strength, devising the shape of the component, or the like, if the side wall portion <NUM> is easily buckled and deformed due to flexing deformation caused by the thinning, the structural member <NUM> cannot exhibit excellent three-point bending characteristics. Further, on the contrary, even if the deformation resistance of the side wall portion <NUM> in a direction intersecting the longitudinal direction Z is increased by increasing the strength, devising the shape of the component, or the like, if the joining member <NUM> is easily buckled and deformed due to flexing deformation caused by the thinning, the structural member <NUM> cannot exhibit excellent three-point bending characteristics. According to the structural member <NUM> of the present embodiment, as described above, the deformation resistance of the top sheet portion <NUM>, the side wall portion <NUM>, and the joining member <NUM> can be exhibited in a complex manner, and thus even if a thinned high-strength material is used, excellent collision safety performance can be exhibited.

In the structural member <NUM> according to the first embodiment, two first beads are formed on the top sheet facing portion <NUM>, but as in a structural member 100A of a first modification example shown in <FIG>, one first bead 150A may be formed on the top sheet facing portion <NUM>.

In the structural member <NUM> according to the first embodiment, the second bead <NUM> is formed from the second corner portion <NUM> to the first corner portion <NUM>, but as in a structural member 100B of a second modification example shown in <FIG>, a second bead 160B may be formed only in the center of the side wall portion <NUM> in the height direction.

Further, the second bead <NUM> may extend from the second corner portion <NUM> to the middle of the side wall portion <NUM> in the height direction, or may extend from the first corner portion <NUM> to the middle of the side wall portion <NUM> in the height direction.

In the structural member <NUM> according to the first embodiment, a member in which the first bead is formed on one steel sheet is used as the joining member <NUM>, but as in a structural member 100C of a third modification example shown in <FIG>, a hat channel member that has a pair of flange portions 121C and 121C as the joining portions, a top sheet portion 123C as the top sheet facing portion on which the first bead is formed, and a side wall portion formed between the flange portion 121C and the top sheet portion 123C may be used as a joining member 120C. In this case, the top sheet portion 123C of the joining member 120C corresponds to the top sheet facing portion <NUM> of the structural member <NUM> according to the first embodiment. In the example shown in <FIG>, the side wall portion of the joining member 120C is flat, but a bead extending in the height direction may be formed.

In the example shown in <FIG>, both end portions of each first bead in the width direction X is present in the top sheet portion 123C as the top sheet facing portion, but one end portion of each first bead in the width direction X may be present in the top sheet portion 123C as the top sheet facing portion, and the other end portion thereof may be present in the side wall portion. That is, only a part of the first bead in the width direction X may be present in the top sheet portion 123C as the top sheet facing portion.

The structural member <NUM> according to the present embodiment has a uniform cross section in the longitudinal direction Z, but may have different cross sections in the longitudinal direction Z. For example, the structural member <NUM> may be curved in the longitudinal direction Z, or in the structural member <NUM>, a cross section perpendicular to the longitudinal direction Z may change.

In the structural member <NUM> according to the present embodiment, the cross sections of the first bead <NUM> and the second bead <NUM> are trapezoidal, but the cross sections may be rectangular, semicircular, or wedge-shaped.

Hereinafter, a structural member <NUM> according to a second embodiment of the present invention will be described.

In the structural member <NUM> according to the first embodiment, the first bead <NUM> is formed at a central portion of the top sheet facing portion <NUM> of the joining member <NUM> in the width direction X.

The structural member <NUM> according to the present embodiment is different from the structural member <NUM> according to the first embodiment in that the first bead is formed in the vicinity of the end portion of the top sheet facing portion of the joining member in the width direction X.

The same reference symbols are used for elements that duplicate those described in the first embodiment such as the hat channel member <NUM>, and the description thereof will be omitted.

First, a schematic configuration of the structural member <NUM> according to the present embodiment will be described with reference to <FIG>.

Similar to the structural member <NUM> according to the first embodiment, the structural member <NUM> according to the present embodiment is a component which is assumed to be installed in an automobile in a posture in which the hat channel member <NUM> faces the inside of the automobile and the joining member <NUM> faces the outside of the automobile.

<FIG> is a cross-sectional view along line B-B' of <FIG>. As shown in <FIG>, the joining member <NUM> has a pair of joining portions <NUM> and <NUM> provided at both ends in the width direction X and a top sheet facing portion <NUM> provided at a center in the width direction X.

Two first beads <NUM> and <NUM> in the longitudinal direction Z are formed on the top sheet facing portion <NUM> in parallel in the width direction X.

As shown in <FIG>, each of the first beads <NUM> and <NUM> is formed such that a center of the first bead <NUM> in the width direction is disposed and the first bead <NUM> bulges inward from the top sheet facing portion <NUM> at a vicinity portion P of each of both ends of the top sheet facing portion <NUM> in the width direction X.

More specifically, the vicinity portion P is a region from an inner end portion of the joining portion <NUM> of the joining member <NUM> to a point having a separation distance of <NUM>/<NUM> of a width W of the top sheet facing portion <NUM> in the width direction X in a cross section perpendicular to the longitudinal direction Z of the structural member <NUM>. The inner end portion of the joining portion <NUM> is an end portion of two end portions of the joining portion <NUM> in the width direction X which is closer to an axis of the structural member <NUM> in the cross section perpendicular to the longitudinal direction Z of the structural member <NUM>.

From another point of view, each of the first beads <NUM> and <NUM> may be formed such that a boundary point between the first bead <NUM> and the joining member <NUM> is positioned in a region from the inner end portion of the joining portion <NUM> of the joining member <NUM> to a point having a separation distance of <NUM> and the first bead <NUM> bulges inward from the top sheet facing portion <NUM> in a cross section perpendicular to the longitudinal direction Z.

As described in the first embodiment, a plurality of second beads <NUM> in a direction intersecting the longitudinal direction Z are formed on the pair of side wall portions <NUM> and <NUM> of the hat channel member <NUM> in parallel.

The structural member <NUM> according to the present embodiment described above has a perpendicular cross-section portion that forms the first beads <NUM> and <NUM> and the second bead <NUM> on at least one of the pair of side wall portions <NUM> and <NUM> in a cross section perpendicular to the longitudinal direction Z. According to the structural member <NUM> of the present embodiment, when an impact load from the outside of the automobile is input to the joining member <NUM> and bending deformation occurs in the structural member <NUM>, as shown in <FIG>, the deformation resistance against the compressive stress (A) in the longitudinal direction Z generated in the joining member <NUM>, the deformation resistance against the compressive stress (B) in a direction intersecting longitudinal direction Z generated in the side wall portion <NUM>, and the deformation resistance against the tensile stress (C) in the longitudinal direction Z generated in the top sheet portion <NUM> can be exhibited in a complex manner.

In particular, since the first bead <NUM> is formed in the vicinity portions P at both ends of the top sheet facing portion <NUM> in the width direction X, the second corner portion <NUM> and the first bead <NUM> are disposed with a short distance. Therefore, in a region from the second corner portion <NUM> to the first bead <NUM>, the bending rigidity in the height direction Y of the cross section intersecting the longitudinal direction Z can be effectively improved. Further, since the second corner portion <NUM> is a portion where the compressive stress in the longitudinal direction Z is generated when the bending deformation occurs in the structural member <NUM> like the joining member <NUM>, in a case where the second bead <NUM> formed in the side wall portion <NUM> extends to the vicinity of the second corner portion <NUM>, the deformation resistance to the compressive stress of the second corner portion <NUM> in the longitudinal direction Z is weakened. However, according to the structural member <NUM> of the present embodiment, the first bead <NUM> is formed in the vicinity of the second corner portion <NUM>, and thus the weakening of the deformation resistance to the compressive stress of the second corner portion <NUM> in the longitudinal direction Z can be efficiently compensated. Therefore, as shown in <FIG>, the joining member <NUM> does not undergo large flexing deformation at an early stage, and the flexing of the side wall portion <NUM> can also be curbed. Therefore, the load capacity at the initial stage of the stroke can be dramatically improved, and the collision safety performance can be further improved as compared with the structural member <NUM> according to the first embodiment.

Hereinafter, the effects of the present invention will be specifically described with reference to examples. The examples which will be described below are merely examples of the present invention and do not limit the present invention.

As Examples <NUM> to <NUM>, a simulation model of a structural member constituted by a hat channel member to which a steel sheet having a sheet thickness of <NUM> and a tensile strength of <NUM> GPa class was applied and a joining member to which a steel sheet having a sheet thickness of <NUM> and a tensile strength of <NUM> GPa class was applied was prepared.

In the simulation model of the structural member, the first bead and the second bead were appropriately applied, and the maximum load at the initial stage of the stroke was evaluated by a simulation assuming three-point bending. The basic conditions are as follows. In these examples, an inclination angle of the bead side wall of the first bead was the same as an inclination angle of the side wall portion of the hat channel member.

As shown in <FIG>, the three-point bending conditions were set such that the radius of curvature of the impactor was <NUM> and the separation distance of the support was <NUM>. Table <NUM> shows the bead application conditions and the evaluation results of the maximum load at the initial stage of the stroke.

In Examples <NUM> to <NUM>, the first bead and the second bead were not formed in a complex manner, and thus the effect of improving the deformation resistance could not be exhibited.

On the other hand, in Examples <NUM> to <NUM> in which the first bead and the second bead were formed in a complex manner, the deformation resistance against the compressive stress in the longitudinal direction Z generated in the joining member, the deformation resistance against the compressive stress in a direction intersecting longitudinal direction Z generated in the side wall portion, and the deformation resistance against the tensile stress in the longitudinal direction Z generated in the top sheet portion were exhibited in a complex manner, and the load capacity at the initial stage of the stroke was improved.

Further, when Example <NUM> and Example <NUM> are compared with each other, in Example <NUM> in which one first bead was disposed at each of both end portions, it was shown that the load capacity at the initial stage of the stroke was increased by <NUM> times or more as compared with Example <NUM> in which two first beads were disposed at the central portion.

Further, as Example 1A, in a simulation model of a structural member in which the hat channel member and the joining member of Example <NUM> were changed into a hat channel member to which a steel sheet having a sheet thickness of <NUM> and a tensile strength of <NUM> GPa was applied, the maximum load at the initial stage of the stroke was evaluated by a simulation assuming three-point bending.

Similarly, as Examples 4A, 6A, and 7A, in a simulation model of a structural member in which the hat channel member and the joining member of each of Examples <NUM>, <NUM>, and <NUM> were changed into a hat channel member to which a steel sheet having a sheet thickness of <NUM> and a tensile strength of <NUM> GPa was applied, the maximum load at the initial stage of the stroke was evaluated by a simulation assuming three-point bending.

Then, in a case where the maximum load obtained in Example 1A was set to a reference value of <NUM>, a ratio of the maximum load obtained in each of Examples 4A, 6A, and 7A to the maximum load obtained in Example 1A was calculated.

Further, as Example 1B, in a simulation model of a structural member in which the hat channel member and the joining member of Example <NUM> were changed into a hat channel member to which a steel sheet having a sheet thickness of <NUM> and a tensile strength of <NUM> GPa was applied, the maximum load at the initial stage of the stroke was evaluated by a simulation assuming three-point bending.

Similarly, as Examples 4B, 6B, and 7B, in a simulation model of a structural member in which the hat channel member and the joining member of each of Examples <NUM>, <NUM>, and <NUM> were changed into a hat channel member to which a steel sheet having a sheet thickness of <NUM> and a tensile strength of <NUM> GPa was applied, the maximum load at the initial stage of the stroke was evaluated by a simulation assuming three-point bending.

Then, in a case where the maximum load obtained in Example 1B was set to a reference value of <NUM>, a ratio of the maximum load obtained in each of Examples 4B, 6B, and 7B to the maximum load obtained in Example 1B was calculated.

Further, as Example 1C, in a simulation model of a structural member in which the hat channel member and the joining member of Example <NUM> were changed into a hat channel member to which a steel sheet having a sheet thickness of <NUM> and a tensile strength of <NUM> GPa was applied, the maximum load at the initial stage of the stroke was evaluated by a simulation assuming three-point bending.

Similarly, as Examples 4C, 6C, and 7C, in a simulation model of a structural member in which the hat channel member and the joining member of each of Examples <NUM>, <NUM>, and <NUM> were changed into a hat channel member to which a steel sheet having a sheet thickness of <NUM> and a tensile strength of <NUM> GPa was applied, the maximum load at the initial stage of the stroke was evaluated by three-point bending.

Then, in a case where the maximum load obtained in Example 1C was set to a reference value of <NUM>, a ratio of the maximum load obtained in each of Examples 4C, 6C, and 7C to the maximum load obtained in Example 1C was calculated.

<FIG> is a graph showing the results of Table <NUM> collectively. From this graph, it was shown that according to the present invention, an excellent load capacity could be exhibited at the initial stage of the stroke regardless of the sheet thickness and the strength, and in a case where one first bead was disposed at each of both end portions of the top sheet facing portion, a higher load capacity could be exhibited when the thinning is performed.

In addition, it was shown that even in a case where the hat channel member and the joining member were thinned, the decrease in the deformation resistance due to the decrease in the sheet thickness could be curbed, and even if a thinned high-strength material was used, excellent collision safety performance could be exhibited.

Further, it was shown that the effect of curbing the decrease in the deformation resistance in a case where the hat channel member and the joining member were thinned was prominent in Examples <NUM> and 7B in which one first bead was disposed at each of both end portions of the top sheet facing portion.

Claim 1:
A structural member (<NUM>, 100A, 100B, 100C, <NUM>) for an automobile body, comprising:
a hat channel member (<NUM>) that has
a top sheet portion (<NUM>) extending in a longitudinal direction (Z),
a pair of side wall portions (<NUM>) extending via first corner portions (<NUM>) formed at both end portions of the top sheet portion (<NUM>) in a width direction (X), and
a pair of flange portions (<NUM>) extending via second corner portions (<NUM>) formed at end portions of the pair of side wall portions (<NUM>) on sides opposite to the first corner portions (<NUM>); and
a joining member (<NUM>,120C,<NUM>) that has
a pair of joining portions (<NUM>, <NUM>) joined to the pair of flange portions (<NUM>) of the hat channel member (<NUM>), and
a top sheet facing portion (<NUM>, <NUM>) facing the top sheet portion (<NUM>) of the hat channel member (<NUM>),
wherein a first bead (<NUM>, 150A, <NUM>) extending in the longitudinal direction (Z) is formed on the top sheet facing portion (<NUM>, <NUM>),
wherein two or more second beads (<NUM>, 160B) extending in a direction intersecting the longitudinal direction (Z) are formed on the pair of side wall portions (<NUM>), wherein two or more of the first beads (<NUM>, <NUM>) are formed in parallel in the width direction (X),
wherein the first bead (<NUM>) bulges inward from the top sheet facing portion (<NUM>) in a cross section perpendicular to the longitudinal direction (Z), and
wherein the first bead (<NUM>) is formed such that a center of the first bead (<NUM>) in the width direction (X) is positioned in a region from an inner end portion of the joining portion (<NUM>) of the joining member (<NUM>,<NUM>)
to a point having a separation distance of <NUM>/<NUM> of a width of the top sheet facing portion (<NUM>) in the width direction (X) in a cross section perpendicular to the longitudinal direction (Z), or wherein the first bead (<NUM>) is formed such that a boundary point between the first bead (<NUM>) and the joining member (<NUM>) is positioned in a region from an inner end portion of the joining portion (<NUM>) of the joining member (<NUM>,<NUM>)
to a point having a separation distance of <NUM> in a cross section perpendicular to the longitudinal direction (Z).