Patent Description:
In the related art, Patent Document <NUM> below describes a laser welded lap joint between high strength steel sheets. Patent Document <NUM> below describes a technique postulating that different deformation modes are set without combining reinforcing steel sheet in a complex manner. Patent Document <NUM> below describes a formed member having at least one ridge portion connecting one surface and another surface.

In order to achieve a further reduction in the weight of a vehicle, for example, it is desirable to allow a structural member to have different thicknesses by increasing the sheet thickness of a portion that needs high strength and decreasing the sheet thickness of a portion that does not need high strength. A technique for realizing a structural member having different thicknesses, a blank having different thicknesses is known. As a technique related to the blank having different thicknesses, there are techniques such as tailor rolled blank (TRB) and tailor welded blank (TWB).

TRB is a technique for manufacturing a blank having different thicknesses by causing different thicknesses limited to a rolling direction, but the direction in which a change in thickness occurs is limited to the rolling direction. For this reason, a change in thickness cannot be incurred in directions other than the rolling direction, and it is difficult to achieve free sheet thickness design.

TWB is a technique for manufacturing a blank having different thicknesses by arranging sheet materials having different thicknesses and welding end surfaces corresponding to the contour lines of the sheet materials. In TWB, from the viewpoint of ease of welding and the like, the end surfaces of straight lines are often welded to each other, so that the weld line becomes a straight line. Therefore, it is difficult to achieve free sheet thickness design for each plane region.

Therefore, for example, as described in Patent Document <NUM> and Patent Document <NUM>, it is conceivable to change the sheet thickness for each region by joining the surfaces of a plurality of sheet materials (for example, two sheet materials). However, the technique described in Patent Document <NUM> is used for joint applications by performing laser welding on high strength steel sheets, and is not intended for free sheet thickness design for blanks. In addition, since the technique is used for joint applications, a direction perpendicular to the weld line is postulated as a direction in which a load is applied.

The technique described in Patent Document <NUM> is a technique postulating that a deformation mode is controlled by bonding sheet materials, and is not a technique postulating that a plurality of sheet materials are joined to exhibit a strength equivalent to that of a single sheet.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a novel and improved member and a vehicle frame capable of satisfying both an improvement in collision safety and a demand for a reduction in weight by realizing different thicknesses in a free manner.

In order to solve the above problems, the present disclosure employs the following means.

According to the present invention, it is possible to provide a member and a vehicle frame capable of satisfying both an improvement in collision safety and a demand for a reduction in weight by realizing different thicknesses in a free manner.

In the present specification and the drawings, like constituent elements having substantially the same functional configuration are denoted by like reference numerals, and overlapping description will be omitted.

For example, steel sheets are used to form the vehicle body of a vehicle such as an automobile. The vehicle body is required to have resistance to buckling in order to secure collision characteristics in the event of a collision. At the same time, the vehicle body is also required to have a reduced weight in order to improve its performance as a vehicle. The present embodiment relates to a member used for such a vehicle body and a vehicle frame including the member. In addition, such a member is manufactured by forming a blank. In the present disclosure, the blank is included in the member. This is because the member and the blank as the material of the member have the same characteristics. In the following, there are cases where the member may be replaced with the blank for description.

<FIG> is a schematic view illustrating an example of a member included in a vehicle body, and illustrates a B pillar <NUM> for connection between a floor and a roof between a front seat and a rear seat on a side surface of the vehicle. Here, <FIG> illustrates a state in which the B pillar <NUM> is viewed from a side (outside) of the vehicle.

The resistance to buckling required for the member included in the vehicle body such as the B pillar <NUM> differs depending on the position or region in the member. For example, in the B pillar <NUM>, a range indicated by a region R1 in <FIG> corresponds to a position where there is a high possibility that the bumper or the like of another vehicle may collide when the vehicle collides from the side surface. Therefore, in the region R1, it is desirable that the sheet thickness of the B pillar <NUM> is relatively small so that the impact of the collision can be easily absorbed. By reducing the sheet thickness of the B pillar <NUM> in the region R1, the B pillar <NUM> is deformed (crushed) when the bumper of another vehicle collides and can effectively absorb the impact.

On the other hand, a range indicated by a region R2 has higher stiffness and resistance to buckling than the range indicated by the region R1. Therefore, the range has a function of suppressing deformation (deflection) to the minimum and suppressing the intrusion of the colliding object into the vehicle when the bumper collides. In addition, the range indicated by the region R2 supports the roof of the vehicle, and has a function of suppressing the collapse of the roof and protecting the occupants in a case where the vehicle rolls over or the like. By suppressing the deflection and collapse of the B pillar <NUM> in the range indicated by the region R2, it is possible to reliably protect an occupant inside the vehicle body. Therefore, in the region R2, it is desirable to increase the sheet thickness of the B pillar <NUM> from the viewpoint of securing resistance to buckling and stiffness. By increasing the sheet thickness of the B pillar <NUM> in region R2, in a case where the vehicle rolls over or another vehicle collides, the intrusion of the B pillar <NUM> into the vehicle body is suppressed, and the collapse of the B pillar <NUM> in the longitudinal direction thereof is suppressed. Therefore, the occupant can be reliably protected.

As described above, the resistance to buckling required for the member included in the vehicle body differs depending on the position and region in the member. Therefore, for the blank for forming the member, free sheet thickness design such as increasing the sheet thickness of a portion that needs high resistance to buckling and decreasing the sheet thickness of a portion that does not need high resistance to buckling is required. With such sheet thickness design, only a necessary portion secures a sufficient sheet thickness, so that it is possible to achieve a reduction in the weight of the vehicle body.

On the other hand, as described above, with techniques such as TRB and TWB, free sheet thickness design cannot be achieved, and the sheet thickness is increased even in a portion that does not need resistance to buckling, so that it is difficult to achieve both a further reduction in weight and securing resistance to buckling. In the present embodiment, by realizing a member that enables free sheet thickness design, it is possible to provide a member and a vehicle frame capable of satisfying higher demands for both resistance to buckling and a reduction in weight. The details will be described below.

<FIG> is a perspective view illustrating the configuration of a blank <NUM> according to the present embodiment. As illustrated in <FIG>, the blank <NUM> according to the present embodiment is constituted by a first sheet material <NUM> and a second sheet material <NUM>, and the first sheet material <NUM> and the second sheet material <NUM> are overlapped with each other. All the end portions of the second sheet material <NUM> are inside the first sheet material <NUM> when viewed in a sheet thickness direction. That is, the second sheet material <NUM> is smaller than the first sheet material <NUM>, and a contour line showing the contour of the second sheet material <NUM> is located inside a contour line showing the contour of the first sheet material <NUM>. In addition, all the end portion of the first sheet material <NUM> may be inside the second sheet material <NUM> when viewed in the sheet thickness direction. That is, the first sheet material <NUM> is smaller than the second sheet material <NUM>, and the contour line showing the contour of the first sheet material <NUM> may be located inside the contour line showing the contour of the second sheet material <NUM>.

The second sheet material <NUM> is joined to the first sheet material <NUM>. In the present embodiment, in particular, the first sheet material <NUM> and the second sheet material <NUM> are joined to each other by continuous joining. Here, continuous joining does not include point-shaped joining such as so-called spot welding. The first sheet material <NUM> and the second sheet material <NUM> are joined by continuous line joining.

It is preferable that the first sheet material <NUM> and the second sheet material <NUM> are joined to each other by line welding. However, it is not necessary that all the joint lines of the line welding are continuous, and there may be a region on the extension line of the joint lines where the line welding is not performed. In addition, it is preferable that laser welding is performed as the line welding. <FIG> illustrates a state in which the first sheet material <NUM> and the second sheet material <NUM> are joined to each other by line welding as laser welding. Therefore, three joint line portions <NUM> are formed on the surface of the second sheet material <NUM>. Specifically, the three joint line portions <NUM> each join the first sheet material <NUM> and the second sheet material <NUM> at the interface between the first sheet material <NUM> and the second sheet material <NUM>. In addition, in this specification, there are cases where the "joint line portion" is simply referred to as a "joint line". The joint line <NUM> may be provided along the longitudinal direction of the sheet material having a small contour line (the second sheet material <NUM> in <FIG>). The joint line <NUM> may not be completely continuous, and may partially have an interval of, for example, about <NUM>, preferably about <NUM>. A film such as plating or foil may be interposed between the first sheet material <NUM> and the second sheet material <NUM>.

In <FIG>, although three joint line portions are formed in the sheet material, in a case where ridges are formed in the overlapped members, the joint line portions may be replaced with ridge portions. At the ridge portion, the first sheet material <NUM> and the second sheet material <NUM> may be overlapped with each other. This is because a portion where the ridge of the sheet material is formed is less likely to be curved, and is thus less likely to be deformed as if the sheet material is restrained by the joint line.

In <FIG>, an example in which the blank <NUM> is constituted by the first sheet material <NUM> and the second sheet material <NUM> is illustrated. However, the blank <NUM> may be constituted by three or more sheet materials. In a case where the blank <NUM> is constituted by three or more sheet materials, the presence or absence of joining and the form of joining between the other sheet materials constituting the blank <NUM> and the first sheet material <NUM> and/or the second sheet material <NUM> are not particularly limited as long as the first sheet material <NUM> and the second sheet material <NUM> are appropriately joined by line joining. Furthermore, the blank <NUM> may be constituted by a plurality of sheet materials selected from a plurality of sheet thicknesses. In the present embodiment, a case where the sheet thickness of the first sheet material <NUM> is equal to or less than the sheet thickness of the sheet material of the second sheet material <NUM> will be described as an example.

The first sheet material <NUM> and the second sheet material <NUM> may be sheet materials having different tensile strengths. For example, the first sheet material <NUM> having a larger contour line than the second sheet material <NUM> is a sheet material serving as a base of the blank <NUM>, and the second sheet material <NUM> functions as a reinforcing sheet material. Therefore, the tensile strength of the second sheet material <NUM> may be higher than that of the first sheet material <NUM>.

The first sheet material <NUM> and the second sheet material <NUM> may have different amounts of carbon (amounts of C) contained in the sheet materials. The amount of carbon may be measured at a <NUM>/<NUM> depth position of the sheet thickness of each sheet material from the surface of each sheet material. For example, the blank <NUM> can be formed by being subjected to hot stamping. Here, the tensile strengths of the first sheet material <NUM> and the second sheet material <NUM> after quenching can be changed depending on the amount of C contained in the sheet materials. For example, in a case where the amount of C contained in the second sheet material <NUM> is larger than the amount of C contained in the first sheet material <NUM>, the tensile strength of a portion of the second sheet material <NUM> becomes higher than that of a portion of the first sheet material <NUM> after hot stamping. The tensile strengths of the first sheet material <NUM> and the second sheet material <NUM> are suitably set to <NUM> MPa or more.

The surfaces of the first sheet material <NUM> and the second sheet material <NUM> may be plated with aluminum or the like. However, the surface serving as the joint surface where the first sheet material <NUM> and the second sheet material <NUM> are in close contact with each other does not have to be plated.

According to the blank <NUM> of the present embodiment configured as described above, by joining the second sheet material <NUM> only to the necessary portion on the first sheet material <NUM>, only the portion that needs resistance to buckling (that is, an improvement in collision safety) can be thickened to secure the resistance to buckling, while the sheet thickness of the portion that does not require high resistance to buckling can be reduced. As a result, it is possible to configure the blank <NUM> that enables free sheet thickness design and satisfies both resistance to buckling and the demand for a reduction in weight. The member such as the B pillar <NUM> illustrated in <FIG> is configured by performing press forming on the blank <NUM>.

<FIG> are schematic views illustrating the joint lines <NUM> of line welding in which the first sheet material <NUM> and the second sheet material <NUM> are welded to each other. <FIG> illustrates an example in which the first sheet material <NUM> and the second sheet material <NUM> are joined to each other by three joint lines <NUM> as in <FIG>. <FIG> illustrates an example in which the first sheet material <NUM> and the second sheet material <NUM> are joined to each other by five joint lines <NUM>.

In a case where a load is applied to the blank <NUM> in an arrow A2 direction shown in <FIG>, an initial reaction force is generated. At that time, the sheet material may warp. When the sheet material warps, not the entire cross section of the sheet material receives the load. In order to increase the initial reaction force, it is desirable to suppress the occurrence of warpage and to make regions for receiving the load larger in the cross section in the sheet width direction. The present inventors found that by disposing at least three joint line portions (including ridge portions) at predetermined positions, the warpage of regions surrounded by the joint line portions can be suppressed. The details will be described below.

As illustrated in <FIG>, the first sheet material <NUM> and the second sheet material <NUM> are overlapped with each other, and a first joint line portion 200a, a second joint line portion 200b, and a third joint line portion 200c each join the first sheet material <NUM> and the second sheet material <NUM> at the interface between the first sheet material <NUM> and the second sheet material <NUM>.

<FIG> is a schematic view illustrating different forms of the first joint line portion 200a, the second joint line portion 200b, and the third joint line portion 200c. As illustrated in <FIG>, the first joint line portion 200a includes an A portion <NUM> whose shortest in-plane distance from the second joint line portion 200b is <NUM> times or more and <NUM> times or less the sheet thickness of the first sheet material <NUM>. The second joint line portion 200b includes a B portion <NUM> whose shortest in-plane distance from the first joint line portion 200a is <NUM> times or more and <NUM> times or less the sheet thickness of the first sheet material <NUM>. As illustrated in <FIG>, of the three joint line portion <NUM>, the third joint line portion 200c at the center is in a first region <NUM> interposed between the A portion <NUM> and the B portion <NUM>. The "shortest in-plane distance" is the shortest distance on a path along the sheet materials of the first sheet material <NUM> and the second sheet material <NUM>. In the example illustrated in <FIG>, the shortest in-plane distance is the distance between the first joint line portion 200a and the second joint line portion 200b when the sheet material is viewed in a plan view.

The length of the length component of the third joint line portion 200c in the first region <NUM> in an extension direction α of the intermediate line between the first joint line portion 200a and the second joint line portion 200b is <NUM> or more. The "extension direction of the intermediate line between the first joint line portion 200a and the second joint line portion 200b" is the direction indicated by reference numeral α in <FIG>.

With such a configuration of the three joint line portions <NUM>, the initial reaction force can be increased, and the warpage of the sheet material can be suppressed.

The first joint line portion 200a, the second joint line portion 200b, and the third joint line portion 200c may be a straight line or a curved line. In a case where at least one of the first joint line portion 200a or the second joint line portion 200b is a curved line, the intermediate line between the first joint line portion 200a and the second joint line portion 200b is also a curved line. In a case where the intermediate line is a curved line, the extension direction of the intermediate line cannot be uniquely defined. Therefore, in the present disclosure, in the case where the intermediate line is a curved line, the direction of the straight line connecting the intersection points between the end portions of the first region <NUM> and the intermediate line is regarded as the extension direction of the intermediate line.

Each joint line portion <NUM> may be connected to another joint line portion <NUM> to form one joint line.

As illustrated in <FIG>, the third joint line portion 200c is preferably in a second region <NUM>. The second region <NUM> is a region which is included in the first region <NUM> and is within <NUM>% of the distance between the first joint line portion 200a and the second joint line portion 200b from the intermediate point between the first joint line portion 200a and the second joint line portion 200b on a straight line orthogonal to the intermediate line.

It is preferable that the continuous length of the length component of the third joint line portion 200c in the second region <NUM> in the extension direction of the intermediate line between the first joint line portion 200a and the second joint line portion 200b is <NUM> or more. The "extension direction of the intermediate line between the first joint line portion 200a and the second joint line portion 200b" is the direction indicated by reference numeral α in <FIG>.

As illustrated in <FIG>, it is preferable that the third joint line portion 200c is in a third region <NUM>. The third region <NUM> is a region which is included in the first region <NUM> and is in a range of <NUM> times or less the sheet thickness of the first sheet material <NUM> from the first joint line portion 200a.

It is preferable that the continuous length of the length component of the third joint line portion 200c in the third region <NUM> in the extension direction of the intermediate line between the first joint line portion 200a and the second joint line portion 200b is <NUM> or more.

In <FIG> and <FIG>, three joint line portions are formed in the sheet material. However, in a case where the blank is formed and the member has a shape including a ridge such as a hat type, the joint line portion may be a ridge portion. That is, the joint line portion can be replaced with the ridge portion. For example, the second joint line portion 200b illustrated in <FIG> may be replaced with a ridge portion. By the configuration of the two joint line portions 200a and 200c and the joint line portion 200b which is a ridge, the initial reaction force can be increased, and the warpage of the sheet material can be suppressed. In this case, the third joint line portion 200c may be in a fourth region (not illustrated) which is in the first region <NUM>, and is in a range of <NUM> times or less the sheet thickness of the first sheet material <NUM> from the joint line portion 200b which is the ridge portion. It is preferable that the continuous length of the length component of the third joint line portion 200c in the fourth region in the extension direction of the intermediate line between the first joint line portion 200a and the ridge portion is <NUM> or more. The third joint line portion 200c may also be in the third region <NUM>.

As described above, in order to increase the initial reaction force, it is desirable to suppress the occurrence of warpage and to make the regions for receiving the load larger in the cross section in the sheet width direction. Furthermore, the inventors found that the initial reaction force is increased by the relationship between the sheet thickness and the sheet width of a predetermined sheet material. The details will be described below.

In order to increase the initial reaction force, it is desirable that the width that can receive the load is large in the total sheet width W<NUM> of the sheet material. Therefore, the ratio of the width of the sheet material that can receive the load to the total sheet width W<NUM> of the sheet material is defined as an effective width. Specifically, the effective width is the ratio of the width that acts to receive the load to the total sheet width W<NUM>.

As the sheet width W<NUM> of the sheet material increases, the cross section along the direction of the sheet width W<NUM> widens, and it is more likely to be affected by the warpage (deflection) of the sheet material, so that the effective width decreases. In addition, as the sheet thickness t decreases, the warpage of the sheet material increases, and the ratio of the width that receives the load to the total sheet width W<NUM> decreases. Therefore, as the sheet width W<NUM> increases and the sheet thickness t decreases, the effective width decreases. That is, the effective width decreases as the ratio (W<NUM>/t) of the sheet width W<NUM> to the sheet thickness t increases. <FIG> is a characteristic diagram showing the relationship between the ratio (W<NUM>/t) of the sheet width W<NUM> to the sheet thickness t of a sheet material having a tensile strength of <NUM> MPa and the effective width of the sheet material when restraint is performed to suppress deformation of both ends of the sheet material in an out-of-plane direction, in which W<NUM>/t is shown on the horizontal axis and the effective width is shown on the vertical axis.

As shown in <FIG>, the effective width decreases as W<NUM>/t increases. Therefore, in order to increase the initial reaction force by increasing the effective width, it is desirable to decrease the sheet width and increase the sheet thickness. As shown in <FIG>, in a region where W<NUM>/t is less than <NUM>, the effective width is <NUM>, and the load can be received by the entire sheet width W<NUM>, so that the initial reaction force can be increased.

In other words, in the region where W<NUM>/t is less than <NUM>, the load can be received by the entire sheet width W<NUM>. For this reason, even if two sheet materials are not joined by line welding, each sheet material can receive the load with the entire sheet width W<NUM>, so that an equivalent initial reaction force to that of a single sheet material having the same total sheet thickness can be obtained.

The present inventor focused on this point, and came up with the idea that regarding sheet materials having a W<NUM>/t at which the effective width is smaller than <NUM> in <FIG>, that is, sheet materials having a W<NUM>/t of <NUM> or more, by joining a plurality of sheet materials by welding, for example, it is possible to secure a tensile strength equivalent to that of a sheet material having the same total sheet thickness.

That is, the blank <NUM> according to the present embodiment includes first sheet material <NUM> and the second sheet material <NUM>, and these sheet materials are joined by at least three joint lines. Here, of the three joint lines 200a, 200b, and 200c, in a case where the distance between the two outer joint lines (the distance between the first joint line portion 200a and the second joint line portion 200b) is defined as W, following the relationship between the sheet width W<NUM> and the sheet thickness t described above, the two outer joint lines (the first joint line portion 200a and the second joint line portion 200b) are provided to achieve a W/t value of <NUM> or more, and at least one joint line is provided therebetween. Accordingly, the blank <NUM> having a plurality of regions where the effective width is increased can be obtained. Accordingly, the resistance to buckling is improved. Since the deformation of the ridge in the out-of-plane direction is also suppressed like the joint line, the same effect can be obtained even if the joint line is replaced with the ridge.

In a case where W/t is less than <NUM>, the original effective width is <NUM>, and an action of receiving the load on the entire cross section along the direction of the sheet width W<NUM> is performed. Therefore, even if two sheet materials are not joined, an initial reaction force equivalent to that of a single sheet material having the same total sheet thickness can be obtained. Therefore, in a case where the W/t value is <NUM> or less, the case can be excluded from a method of joining a plurality of sheet materials according to the present embodiment.

On the other hand, when the W/t value is too large, the interval between the joint lines is too large, and there is concern that the effect of providing the joint lines may not be obtained. Referring to <FIG>, it can be estimated that a large effect cannot be obtained when the interval between the joint lines is larger than <NUM> times the sheet thickness. From this, the W/t value is set to <NUM> or less. Then, when the third joint line portion is added between the first joint line portion and the second joint line portion, the interval between the third joint line portion and the first or second joint line portion becomes smaller than <NUM> times the sheet thickness, and an effect of providing the third joint line portion can be obtained. As a result of the examination by the present inventors, it is preferable that the upper limit of W/t is set to <NUM>. Therefore, it is preferable that the W/t value satisfies Expression (<NUM>).

In addition, of any three joint lines, the length of the length component of the joint line portion <NUM> provided between the two outer joint line portions in the extension direction of the intermediate line between the two outer joint lines is <NUM> or more. In a case where the length of the length component of the joint line portion <NUM> in the extension direction of the intermediate line is less than <NUM>, if bending deformation occurs in a portion of the member after forming where the sheet materials are overlapped with each other, an effect of integrating the sheet materials that are overlapped with each other is insufficient, and there is a possibility that bending may occur from unexpected places. The upper limit of the length of the length component of the joint line portion <NUM> in the extension direction of the intermediate line is not particularly limited, and can be set according to the shape of the sheet material to be used, the portion to be welded, and the like. The "extension direction of the intermediate line between the two outer joint line portions" is the direction indicated by reference numeral α in <FIG>, as described with reference to <FIG>.

In addition, of the joint lines <NUM> provided in the blank <NUM>, when the distance between any two adjacent joint lines is defined as W', W'/t may be <NUM> or less. As shown in <FIG>, in a case where W<NUM>/t is <NUM> or less, the effective width is about <NUM> or more. Therefore, dividing a region by a weld line improves the effective width. As a result, the warpage of the sheet material is suppressed, and the initial reaction force can be sufficiently increased. Therefore, when W'/t is <NUM> or less after dividing a region, the warpage of the region surrounded by the two adjacent joint lines is suppressed, and the effect of integration can be further obtained. It is preferable that W'/t is less than <NUM>. Accordingly, the effective width in a case where the region surrounded by the two adjacent joint lines is regarded as one sheet material is <NUM>, so that the warpage of the region surrounded by the joint lines can be further suppressed. Accordingly, the effect of integration can be further obtained.

The configuration of the blank (member) <NUM> according to the present embodiment has been described above. For example, in a case where the B pillar <NUM> as illustrated in <FIG> is formed of the blank <NUM> of the present embodiment, in the region R2 in which it is necessary to suppress deflection at the time of a collision, the second sheet material <NUM> having a large sheet thickness may be joined to the first sheet material <NUM> which is the substrate, whereby high stiffness is secured. Here, by applying the portion of the blank <NUM> according to the present embodiment where the second sheet material <NUM> is provided to the region R2, the region R2 can exhibit characteristics (for example, bending) equivalent to those in a case of being formed of a blank with a single sheet. Accordingly, free sheet thickness design of the B pillar <NUM> is possible, so that it is possible to secure resistance to buckling (that is, an improvement in collision safety), and achieve a reduction in weight.

Next, a vehicle frame for a vehicle, which is a hat-shaped member according to an embodiment, will be described. <FIG> is a schematic view illustrating an example of a vehicle frame manufactured by press-forming the blank (member) <NUM> of <FIG> into the B pillar <NUM> illustrated in <FIG>. Similar to <FIG>, <FIG> illustrates a state in which the B pillar <NUM> is viewed from the side (outside) of the vehicle. Similar to <FIG>, the region R1 and the region R2 are also illustrated in <FIG>. In the example illustrated in <FIG>, the B pillar <NUM> is formed of the blank <NUM> according to the present embodiment, and a second member <NUM> is joined to a first member <NUM> which is the substrate, in the region R2. The first member <NUM> corresponds to after processing of the first sheet material <NUM> included in the blank <NUM>, and the second member <NUM> corresponds to after processing of the second sheet material <NUM> included in the blank <NUM>. In this case, as illustrated in <FIG>, the entire surface of the second member <NUM> facing the first member <NUM> may face the first member <NUM>.

<FIG> are schematic views illustrating vehicle frames formed of the blank (member) <NUM> of the embodiment. The members illustrated in <FIG> may be replaced with hat-shaped members as illustrated in <FIG>. A vehicle frame <NUM> is a member extending in a predetermined direction, and <FIG> and 7D to <NUM> illustrate cross-sectional shapes in a direction orthogonal to the extension direction. As illustrated in <FIG>, the vehicle frame <NUM> includes a ridge portion <NUM>, a top wall portion <NUM>, and a standing wall portion <NUM> formed by bending the blank <NUM>.

The vehicle frame <NUM> is constituted by the first member <NUM> and the second member <NUM>, and the first member <NUM> and the second member <NUM> are overlapped with each other. The first member <NUM> has a top wall portion <NUM> extending in the longitudinal direction of the hat-shaped member. The second member <NUM> has a top wall portion <NUM> extending in the longitudinal direction of the hat-shaped member. The sheet thickness of the first member <NUM> is equal to or less than the sheet thickness of the sheet material of the second member <NUM>.

In the vehicle frame <NUM> illustrated in <FIG>, in the top wall portion <NUM> (the top wall portion <NUM> of the first member <NUM> and the top wall portion <NUM> of the second member), the first member <NUM> and the second member <NUM> are welded to each other at the three joint line portions <NUM> (the first joint line portion 200a, the second joint line portion 200b, and a fourth joint line portion 200d). In this specification, there are cases where the "joint line portion" may be simply referred to as a "joint line". The joint lines 200a, 200b, and 200d are formed along a direction in which the vehicle frame <NUM> extends. The first joint line portion 200a and the second joint line portion 200b are provided at the two ridge portions <NUM> (a first ridge portion 610a and a second ridge portion 610b) of the first member <NUM> and the second member <NUM>. Of the two ridge portions 610a and 610b, the first ridge portion 610a is a ridge portion 610a of one ends of the top wall portion <NUM> of the first member <NUM> and the top wall portion <NUM> of the second member <NUM>, at which the first member <NUM> and the second member <NUM> are overlapped with each other. The second ridge portion 610b is a ridge portion 610b of the other ends of the top wall portion <NUM> of the first member <NUM> and the top wall portion <NUM> of the second member <NUM>, at which the first member <NUM> and the second member <NUM> are overlapped with each other.

The three joint line portions <NUM> (the first joint line portion 200a, the second joint line portion 200b, and the fourth joint line portion 200d) join the first member <NUM> and the second member <NUM> at the interface between the first member <NUM> and the second member <NUM>.

As illustrated in <FIG>, the first ridge portion 610a includes a C portion <NUM> whose shortest in-plane distance from the second ridge portion 610b is <NUM> times or more and <NUM> times or less the sheet thickness of the first member <NUM>. The second ridge portion 610b includes a D portion <NUM> whose shortest in-plane distance from the first ridge portion 610a is <NUM> times or more and <NUM> times or less the sheet thickness of the first member <NUM>. The fourth joint line portion 200d is in a fifth region <NUM> interposed between the C portion <NUM> and the D portion <NUM>. The "shortest in-plane distance" is the shortest distance on a path along the members of the first member <NUM> and the second member <NUM>. In <FIG>, the "shortest in-plane distance" is a line length along the outer surface in a cross section crossing the longitudinal direction of the member.

The continuous length of the length component of the fourth joint line portion 200d in the fifth region <NUM> in an extension direction of the intermediate line between the first ridge portion 610a and the second ridge portion 610b is <NUM> or more. The "extension direction of the intermediate line between the first ridge portion 610a and the second ridge portion 610b" means the direction indicated by reference numeral α when the first joint line portion 200a and the second joint line portion 200b in <FIG> are replaced with the ridge portions <NUM>.

In the vehicle frame <NUM> described above, the top wall portion <NUM> of the first member <NUM> and the top wall portion <NUM> of the second member <NUM> are disposed so as to be on the outside of the vehicle.

With such a vehicle frame <NUM>, the top wall portion <NUM> of the first member <NUM> and the top wall portion <NUM> of the second member <NUM> are more firmly adhered to each other, and the resistance to buckling of a portion where the top wall portion <NUM> and the top wall portion <NUM> are joined to each other can be efficiently increased.

It is preferable that the fourth joint line portion 200d is in a sixth region (not illustrated). The sixth region is a region which is included in the fifth region and is within <NUM>% of the distance between the first ridge portion 610a and the second ridge portion 610b from the intermediate point between the first ridge portion 610a and the second ridge portion 610b on a straight line orthogonal to the intermediate line.

It is preferable that the continuous length of the length component of the fourth joint line portion 200d in the sixth region in the extension direction of the intermediate line between the first ridge portion 610a and the second ridge portion 610b is <NUM> or more.

It is preferable that the fourth joint line portion 200d is in a seventh region (not illustrated) which is in the fifth region and is in a range of <NUM> times or less the sheet thickness of the first sheet material <NUM> from the first ridge portion 610a.

It is preferable that the continuous length of the length component of the fourth joint line portion 200d in the fifth region in the extension direction of the intermediate line between the first ridge portion 610a and the second ridge portion 610b is <NUM> or more.

In the vehicle frame <NUM> illustrated in <FIG>, the first member <NUM> and the second member <NUM> are welded to each other at the three joint line portions 200a, 200b, and 200d in the top wall portion <NUM>, whereas in the vehicle frame <NUM> illustrated in <FIG> and <FIG>, the first member <NUM> and the second member <NUM> are welded to each other at the one fourth joint line portion 200d in the top wall portion <NUM>. In the vehicle frame <NUM> of <FIG>, the first joint line portion 200a located at the first ridge portion 610a and the second joint line portion 200b located at the second ridge portion 610b of the vehicle frame <NUM> can be omitted. Since the first member <NUM> and the second member <NUM> are engaged with each other at the first ridge portion 610a and the second ridge portion 610b, the ridge portions 610a and 610b exhibit the same effect as the first joint line portion 200a and the second joint line portion 200b. That is, it is possible to replace the joint line portion with the ridge portion. Therefore, as illustrated in <FIG> and <FIG>, for example, the ridge portions 610a and 610b are not provided with the joint line portions, and the first member <NUM> and the second member <NUM> may be joined to each other by only one fourth joint line portion 200d. By not providing the joint line portions 200a and 200b at the ridge portions 610a and 610b, it is possible to reduce the possibility that cracking may occur at the ridge portions 610a and 610b when the vehicle frame <NUM> is deformed. Further, the number of joint line portions to be installed can be reduced, and a reduction in cost or strengthening of the joining of the top wall portions <NUM> and <NUM> can be achieved.

As illustrated in <FIG>, the ridge portions 610a and 610b are not provided with the joint line portions, and in the top wall portion <NUM> (the top wall portion <NUM> of the first member <NUM> and the top wall portion <NUM> of the second member), the first member <NUM> and the second member <NUM> may be joined to each other at only the three joint line portions <NUM> (the first joint line portion 200a, the second joint line portion 200b, and the fourth joint line portion 200d). In the vehicle frame <NUM> illustrated in <FIG>, the first joint line portion 200a and the second joint line portion 200b also correspond to the ridge portion <NUM> extending in the longitudinal direction. Furthermore, as illustrated in <FIG>, the top wall portion <NUM> is provided with three or more joint line portions <NUM> (the first joint line portion 200a, the second joint line portion 200b, and the fourth joint line portion 200d). Therefore, the strain at the joint line portion <NUM> in the top wall portion <NUM> can be dispersed, and a higher load can be withstood.

As illustrated in <FIG>, the top wall portion <NUM> of the vehicle frame <NUM> (the top wall portion <NUM> of the first member <NUM> and the top wall portion <NUM> of the second member) may be provided with the fourth joint line portion 200d on, and the standing wall portion <NUM> connected to the top wall portion <NUM> via the ridge portion <NUM> may also be provided with the joint line portions <NUM> (the first joint line portion 200a and the second joint line portion 200b). Even in this case, the ridge portion <NUM> exhibits the same effect as the joint line portions <NUM> (the first joint line portion 200a and the second joint line portion 200b), so that the ridge portion <NUM> can be regarded as the joint line portions <NUM> (the first joint line portion 200a and the second joint line portion 200b).

<FIG> illustrates an example in which the first member <NUM>, which is a hat-shaped member having a flange portion, is disposed on the outside, and the U-shaped second member <NUM> is disposed on the inside as a reinforcing member. In the example of <FIG>, similarly to <FIG>, the first member <NUM> and the second member <NUM> are welded to each other at the three joint line portions <NUM> (the first joint line portion 200a, the second joint line portion 200b, and the fourth joint line portion 200d).

<FIG> illustrates an example in which the first member <NUM>, which is a hat-shaped member having a flange portion, is disposed on the inside, and the U-shaped second member <NUM> is disposed on the outside as a reinforcing member. In the example of <FIG>, similarly to <FIG>, the first member <NUM> and the second member <NUM> are also welded to each other at the three joint line portions <NUM> (the first joint line portion 200a, the second joint line portion 200b, and the fourth joint line portion 200d).

In the vehicle frame <NUM> illustrated in <FIG>, in the top wall portion <NUM>, the first member <NUM> and the second member are welded to each other at two joint line portions <NUM> (the fourth joint line portion 200d and a fifth joint line portion 200e). The two joint line portions <NUM> (the fourth joint line portion 200d and the fifth joint line portion 200e) join the first member <NUM> and the second member <NUM> at the interface between the first member <NUM> and the second member <NUM>.

In <FIG>, the fourth joint line portion 200d includes an E portion (not illustrated) whose shortest in-plane distance from the second ridge portion 610b is <NUM> times or more and <NUM> times or less the sheet thickness of the first member <NUM>. The second ridge portion 610b includes an F portion (not illustrated) whose shortest in-plane distance from the fourth joint line portion 200d is <NUM> times or more and <NUM> times or less the sheet thickness of the first member <NUM>. The fifth joint line portion 200e is in an eighth region (not illustrated) interposed between the E portion and the F portion. In the example illustrated in <FIG>, the "shortest in-plane distance" is the distance between the fourth joint line portion 200d and the second ridge portion 610b when the top wall portion <NUM> is viewed in a plan view.

The continuous length of the length component of the fifth joint line portion 200e in the eighth region in an extension direction of the intermediate line between the second ridge portion 610b and the fourth joint line portion 200d is <NUM> or more. The "extension direction of the intermediate line between the second ridge portion 610b and the fourth joint line portion 200d" is the direction indicated by reference numeral α when the joint line portion 200b in <FIG> is replaced with the ridge portion 610b.

It is preferable that the fifth joint line portion 200e is in a ninth region (not illustrated). The ninth region is a region which is included in the eighth region and is within <NUM>% of the distance between the second ridge portion 610b and the fourth joint line portion 200d from the intermediate point between the second ridge portion 610b and the fourth joint line portion 200d on a straight line orthogonal to the intermediate line.

It is preferable that the continuous length of the length component of the fifth joint line portion 200e in the ninth region in the extension direction of the intermediate line between the second ridge portion 610b and the fourth joint line portion 200d is <NUM> or more.

It is preferable that the fifth joint line portion 200e is in a tenth region (not illustrated) which is in the eighth region and is in a range of <NUM> times or less the sheet thickness of the first sheet material <NUM> from the second ridge portion 610b.

The relationship between the sheet thickness and the sheet width of the sheet material in the embodiment described above will be described in detail below.

In the region R2 of the B pillar <NUM> illustrated in <FIG>, a top wall portion <NUM> of the B pillar is provided with at least three joint line portions <NUM> (200a, 200b, and 200c) along the longitudinal direction of the B pillar <NUM>. W/t represented by the distance W between the two outer joint line portions (200a and 200b) of the three joint line portions and the smaller sheet thickness t of the first member <NUM> and the second member <NUM>, and the length of the joint line portion 200c satisfy the requirements of the above-described embodiment. That is, at least three joint line portion in which <NUM> ≤ W/t ≤ <NUM> is satisfied and the length of the length component of the joint line portion 200c in the extension direction of the intermediate line between the joint line portion 200a and the joint line portion 200b is <NUM> or more are provided in the top wall portion <NUM> of the B pillar <NUM>.

Such a B pillar <NUM> can be manufactured, for example, by press-forming the blank <NUM> according to the above-described embodiment. Specifically, the B pillar <NUM> can be obtained by trimming the blank <NUM> according to the embodiment into a shape to be formed into the B pillar <NUM> and performing general press forming on the trimmed blank <NUM>. For example, the B pillar <NUM> may be provided by separately press-forming the first sheet material <NUM> and the second sheet material <NUM> to form the first member <NUM> and the second member <NUM>, overlapping the first member <NUM> and the second member <NUM>, and then joining both the members by a laser or the like so that joint lines satisfying the above-mentioned requirements are provided. However, by using the blank <NUM> according to the above embodiment, the B pillar <NUM> can be obtained only by press-forming the blank <NUM> once.

Hereinafter, the vehicle frame <NUM> formed of the blank <NUM> of the present embodiment will be described. Here, also in the B pillar <NUM> illustrated in <FIG> or the vehicle frame <NUM> described below, as in the case of the blank described above, resistance to buckling (that is, an improvement in collision safety) can be improved by defining the W/t value.

That is, the B pillar <NUM> according to the present embodiment has the first member <NUM> and the second member <NUM>, and these members are joined to each other by at least three joint lines. Here, in a case where the distance between the two outer joint lines of the three joint lines is defined as W, the outer joint lines are provided so that the W/t value is <NUM> or more, and at least one joint line is provided therebetween, whereby the B pillar <NUM> or the vehicle frame <NUM> having a plurality of regions where the effective width is increased can be obtained. Accordingly, the resistance to buckling is improved.

On the other hand, when the W/t value is too large, the interval between the joint lines is too large, and there is concern that the effect of providing the joint lines may not be obtained. Referring to <FIG>, it can be estimated that a large effect cannot be obtained when the interval between the joint lines is larger than <NUM> times the sheet thickness. From this, the W/t value is set to <NUM> or less. Then, when the joint line is added between the outer joint lines, the interval between the outer joint lines and the joint line added between the outer joint lines becomes smaller than <NUM> times the sheet thickness, and an effect of providing the joint line added between the outer joint lines can be obtained. Therefore, as a result of the examination by the present inventors, like the blank <NUM>, it is preferable that the upper limit of W/t is set to <NUM> also in the B pillar <NUM> or the vehicle frame <NUM>.

In addition, of any three joint lines, the length of the length component of the joint line portion <NUM> provided between the two outer joint line portions <NUM> in the extension direction of the intermediate line between the two outer joint lines is <NUM> or more. In a case where the length of the length component of the joint line portion <NUM> in the extension direction of the intermediate line is less than <NUM>, if bending deformation occurs in a portion of the member after forming where the sheet materials are overlapped with each other, an effect of integrating the sheet materials that are overlapped with each other is insufficient, and there is a possibility that bending may occur from unexpected places. The upper limit of the length of the length component of the joint line portion <NUM> in the extension direction of the intermediate line is not particularly limited, and can be set according to the shape of the sheet material to be used, the portion to be welded, and the like.

Furthermore, the B pillar <NUM> or the vehicle frame <NUM> may be constituted by a plurality of members selected from a plurality of sheet thickness, or may be constituted by a plurality of members having substantially the same sheet thickness.

The first member <NUM> and the second member <NUM> may be members having different tensile strengths. For example, the first member <NUM> is a main frame member of the B pillar <NUM> or the vehicle frame <NUM>, and the second member <NUM> functions as a reinforcing member. Therefore, the tensile strength of the second member <NUM> may be higher than the tensile strength of the first member <NUM>. The tensile strength of the first member <NUM> is suitably set to <NUM> MPa or more. The tensile strength of the second member <NUM> is suitably set to <NUM> MPa or more.

The first member <NUM> and the second member <NUM> may have different amounts of carbon (amounts of C) contained in the sheet materials. The amount of carbon may be measured at a <NUM>/<NUM> depth position of the sheet thickness of each member from the surface of each member. For example, the B pillar <NUM> or the vehicle frame <NUM> is obtained by subjecting the blank <NUM> described above to hot stamping.

The surfaces of the first member <NUM> and the second member <NUM> may be plated with aluminum or the like. However, the surface serving as the joint surface where the first member <NUM> and the second member <NUM> are in close contact with each other does not have to be plated.

In addition, as described in the embodiment relating to the blank, of the joint lines <NUM>, when the distance between any two adjacent joint lines is defined as W', W'/t may be <NUM> or less.

<FIG> is a diagram showing an automobile frame <NUM> as an example to which the blank <NUM> and the vehicle frame <NUM> according to the present embodiment are applied. The vehicle frame <NUM> formed of the blank <NUM> may form the automobile frame <NUM> as a cabin frame or a shock absorbing frame. Application examples of the vehicle frame <NUM> as the cabin frame include a roof center reinforcement <NUM>, a roof side rail <NUM>, a B pillar <NUM>, a side sill <NUM>, a tunnel <NUM>, an A pillar lower <NUM>, an A pillar upper <NUM>, a kick reinforcement <NUM>, and a floor cross member <NUM>, an under reinforcement <NUM>, and a front header <NUM>.

Application examples of the vehicle frame <NUM> as the shock absorbing frame include a rear side member <NUM>, an apron upper member <NUM>, a bumper reinforcement <NUM>, a crash box <NUM>, and a front side member <NUM>.

When the vehicle frame <NUM> formed of the blank <NUM> is used as the cabin frame or the shock absorbing frame, since the sheet thickness for each region of the blank <NUM> is optimally adjusted, the vehicle frame <NUM> has a sufficient load capacity. Furthermore, since the sheet thickness for each region of the blank <NUM> is optimally adjusted, the impact absorption capacity and proof stress of the vehicle frame <NUM> are enhanced, so that even in a case where a side collision or like is input to the automobile frame <NUM>, the amount of intrusion of the vehicle frame <NUM> into the vehicle can be suppressed while absorbing the impact by sufficient deformation. In addition, it is also possible to use the blank <NUM> as it is for an automobile frame such as in a case of use for a floor panel of an automobile. Even in this case, free design such as increasing the sheet thickness of only a portion that needs stiffness in the floor panel can be realized.

While the example in which the blank <NUM> and the vehicle frame <NUM> are applied to the automobile frame <NUM> has been described, the present disclosure is not limited thereto. The blank <NUM> and the vehicle frame <NUM> can be applied to a frame included in vehicles other than automobiles. Alternatively, the blank <NUM> and the vehicle frame <NUM> can also be applied to a structure included in a building or the like.

The present inventors intensively examined the effect of a welding form in the blank <NUM> and the number of joint lines <NUM> on the initial reaction force with respect to the load. <FIG> is a diagram showing the effect of the welding form and the number of joint lines <NUM> on the initial reaction force. In <FIG>, the initial reaction force generated in a case where a load is applied to the end surface of the blank <NUM> in a direction (the direction along the joint line <NUM>, arrow A2 direction illustrated in <FIG>) orthogonal to the width direction using a sheet material having a sheet width W<NUM> of <NUM> is represented on the vertical axis.

Here, in the example shown in <FIG>, a sheet material having a tensile strength of about <NUM> MPa was used, and Sample <NUM> formed of one sheet material having a sheet thickness of <NUM> and samples (Samples <NUM> to <NUM>) in which two sheet materials having a sheet thickness of <NUM> were overlapped with each other were prepared. That is, in Samples <NUM> to <NUM>, the total sheet thickness of the two sheets is the same as the sheet thickness of Sample <NUM>. Sample <NUM> is obtained by overlapping the two sheet materials and performing line welding on only both ends of the sheet materials. Samples <NUM> to <NUM> had the two sheet materials joined by welding, but were different in the welding method (the number of joint lines and the like). In Sample <NUM>, line welding was performed on a total of three joint lines <NUM> in both end portions and the center portion of the sheet materials, in Sample <NUM>, line welding was performed on a total of four joint lines <NUM> in both end portions and the center portion of the sheet materials, and in Sample <NUM>, line welding was performed on a total of five joint lines <NUM> in both end portions and the center portion of the sheet materials. In Sample <NUM>, line welding was performed on both end portions of the sheet materials, and spot welding was performed on the center portion along a total of three imaginary lines with a nugget diameter of <NUM>√t (t is the sheet thickness (mm) of a thinner sheet material, that is, <NUM>) at a pitch of <NUM>. Laser welding was performed as the line welding. Then, for each of Samples <NUM> to <NUM>, the initial reaction force in a case where a load was applied in the direction orthogonal to the sheet width W<NUM> was measured. Since the outer joint lines <NUM> were provided in the vicinity of both end portions of the sheet material, the sheet width W<NUM> is substantially equal to the distance W between the two outer joint lines.

As shown in <FIG>, in Sample <NUM>, the initial reaction force was about <NUM> [kN]. In Sample <NUM>, although the total sheet thickness was <NUM>, which was the same as in Sample <NUM>, the initial reaction force did not reach <NUM> [kN], and the initial reaction force was less than half that of Sample <NUM>.

As shown in Samples <NUM> to <NUM>, the initial reaction force increased as the number of joint lines <NUM> increased. In Sample <NUM>, an initial reaction force equivalent to that in Sample <NUM> was obtained. On the other hand, in Sample <NUM> in which spot welding was performed, although spot welding was performed along three lines, only an initial reaction force lower than that of sample <NUM> was obtained, and an initial proof stress equivalent to that of Sample <NUM> was obtained.

From the above results, it was found that in a case where the two sheet materials are welded by line welding, the initial proof stress can be improved by providing at least three joint lines <NUM>. In particular, it could be seen that by providing three or more joint lines <NUM> in addition to the outer joint lines <NUM>, it is possible to secure a tensile strength equivalent to that of a single sheet material having the same sheet thickness as the total sheet thickness of two sheet materials. It is considered that this is due not only to the effect of expanding an effective region of the sheet materials, but also to a reduction in the possibility of fracture of the joint lines caused by the dispersion of strain to the joint lines.

While the preferred embodiments of the present disclosure have been described above in detail with reference to the accompanying drawings, the present disclosure is not limited to such examples.

Claim 1:
A member (<NUM>) comprising:
a first sheet material (<NUM>);
a second sheet material (<NUM>);
a first joint line portion (200a);
a second joint line portion (200b); and
a third joint line portion (200c),
wherein a sheet thickness of the first sheet material (<NUM>) is equal to or less than a sheet thickness of the second sheet material (<NUM>),
the first sheet material (<NUM>) and the second sheet material (<NUM>) are overlapped with each other,
the first joint line portion (200a), the second joint line portion (200b), and the third joint line portion (200c) each join the first sheet material (<NUM>) and the second sheet material (<NUM>) at an interface between the first sheet material (<NUM>) and the second sheet material (<NUM>),
the first joint line portion (200a) includes an A portion (<NUM>) whose shortest in-plane distance from the second joint line portion (200b) is <NUM> times or more and <NUM> times or less the sheet thickness of the first sheet material (<NUM>),
the second joint line portion (200b) includes a B portion (<NUM>) whose shortest in-plane distance from the first joint line portion (200a) is <NUM> times or more and <NUM> times or less the sheet thickness of the first sheet material (<NUM>),
the third joint line portion (200c) is in a first region (<NUM>) interposed between the A portion (<NUM>) and the B portion (<NUM>),
a length of a length component of the third joint line portion (200c) in the first region (<NUM>) in an extension direction of an intermediate line between the first joint line portion (200a) and the second joint line portion (200b) is <NUM> or more, and characterized in that at least one of the first j oint line portion (200a) or the second joint line portion (200b) is a curved line and the third joint line portion (200c) between the first joint line portion (200a) and the second joint line portion (200b) is also a curved line.