JP6794792B2 - Structural members for automobiles and their manufacturing methods - Google Patents

Description

The present invention relates to structural members for automobiles and methods for manufacturing the same.

The body of an automobile is composed of various connected structural members. Most structural members are formed by press forming a steel sheet. In recent years, structural members of automobiles (particularly long members) are required to have high characteristics in a three-point bending test in order to improve collision safety performance. Therefore, various proposals have been made conventionally.

For example, the figures of Patent Document 1 (Japanese Patent Laid-Open No. 2008-265609) and Patent Document 2 (Japanese Patent Laid-Open No. 2008-155479) disclose a shock absorbing member including a portion in which steel plates are triple-folded. ing.

Patent Document 3 (Japanese Unexamined Patent Publication No. 2011-67841) cites a cross-section hat-shaped part having a large number of ridges in the cross section as an example of a part having high collision safety. Patent Document 4 (Japanese Unexamined Patent Publication No. 2013-27894) discloses a frame component having a reinforcing portion formed at a connecting portion between the top wall portion and the vertical wall portion. This reinforcing portion is composed of an overlapping portion that is rolled into a tubular shape.

Currently, there is a demand for structural members capable of further enhancing collision safety performance. Further, at present, it is required to increase the degree of freedom of the method of fixing the structural member. Double-sided spot welding, in which electrode rods are pressed from both sides of the welded portion to perform resistance spot welding, is a low-cost and highly reliable welding method. However, when welding another structural member to the hollow structural member, it may be difficult to pass the electrode rod through the hollow structural member. As a method of performing resistance spot welding in such a case, Patent Document 5 (Japanese Unexamined Patent Publication No. 2013-169590) describes a method of one-sided spot welding in which an electrode rod is pressed from only one side of a welded portion to perform resistance spot welding. It is disclosed.

However, in one-sided spot welding, control of pressing force and energization path is complicated, and the cost tends to be high. In addition, reliability may be inferior to that of spot welding on both sides.

Japanese Unexamined Patent Publication No. 2008-265609 Japanese Unexamined Patent Publication No. 2008-155479 Japanese Unexamined Patent Publication No. 2011-67841 Japanese Unexamined Patent Publication No. 2013-27894 Japanese Unexamined Patent Publication No. 2013-169590

In such a situation, one of the objects of the present invention is to provide a structural member for an automobile and a method for manufacturing the same, which can enhance collision safety performance and have a high degree of freedom in a method of connecting the constituent members to each other. Is.

The structural member according to one embodiment of the present invention is a structural member for automobiles. This structural member includes a press-molded product formed of one steel plate and a metal member made of a metal plate fixed to the press-molded product. The press-molded product has at least one boundary portion of two vertical wall portions, a top plate portion connecting the two vertical wall portions, and two boundary portions connecting the vertical wall portion and the top plate portion. Includes a protrusion that protrudes from. In the protruding portion, the steel plate extending from the vertical wall portion and the steel plate extending from the top plate portion project from the boundary portion so as to be overlapped by the overlapping portion at least at the tip of the protruding portion. The metal member is fixed to the overlapping portion.

The manufacturing method according to the embodiment of the present invention is the manufacturing method of the structural member according to the above embodiment. This manufacturing method includes a first step of forming a preformed product including the two vertical wall portions and the top plate portion by deforming a material steel plate, and press molding the preformed product. This includes a second step of forming the press-molded product and a third step of fixing the metal member to the overlapping portion of the press-molded product. The premolded article includes a surplus portion for forming the protruding portion. In the second step, the overlapped portion is formed by superimposing at least a part of the material steel sheets constituting the surplus portion.

According to the present invention, it is possible to obtain a structural member for an automobile, which can enhance collision safety performance and has a high degree of freedom in a method of connecting the constituent members to each other.

FIG. 1 is a perspective view schematically showing an example of the structural member of the present embodiment. FIG. 2 is a cross-sectional view schematically showing the structural member shown in FIG. FIG. 3 is a cross-sectional view schematically showing an example of a press-molded product (P). FIG. 4 is a perspective view schematically showing another example of the press-molded product (P). FIG. 5 is a cross-sectional view for explaining a modified example of the press-molded product (P). FIG. 6 is a perspective view schematically showing another example of the press-molded product (P). FIG. 7 is a cross-sectional view schematically showing the press-molded product (P) shown in FIG. FIG. 8A is a cross-sectional view schematically showing an example of a part of the structural members of the present embodiment. FIG. 8B is a cross-sectional view schematically showing an example of a part of the structural members of the present embodiment. FIG. 8C is a cross-sectional view schematically showing an example of a part of the structural members of the present embodiment. FIG. 9A is a perspective view schematically showing another example of the structural member of the present embodiment. FIG. 9B is a diagram schematically showing a partial cross section of FIG. 9A. FIG. 9C is a diagram schematically showing an example of a manufacturing process of a structural member having the same structure as that of FIG. 9B. FIG. 10 is a perspective view schematically showing another example of the structural member of the present embodiment. FIG. 11A is a cross-sectional view schematically showing another example of the structural member of the present embodiment. FIG. 11B is a cross-sectional view schematically showing another example of the structural member of the present embodiment. FIG. 12A is a diagram illustrating the functions of the structural members shown in FIG. 11A. FIG. 12B is a diagram illustrating the functions of the structural members shown in FIG. 11A. FIG. 13 is a cross-sectional view schematically showing an example of a preformed product formed in the manufacturing method of the present embodiment. FIG. 14A is a cross-sectional view schematically showing one step in the second step in an example of the manufacturing method of the present embodiment. FIG. 14B is a cross-sectional view schematically showing one step following the one step of FIG. 14A. 14C is a cross-sectional view schematically showing one step following one step of FIG. 14B. FIG. 14D is a cross-sectional view schematically showing one step following the one step of FIG. 14C. FIG. 15A is a cross-sectional view schematically showing one step of the second step in another example of the manufacturing method of the present embodiment. FIG. 15B is a cross-sectional view schematically showing one step following the one step of FIG. 15A. FIG. 15C is a cross-sectional view schematically showing one step following the one step of FIG. 15B. FIG. 15D is a cross-sectional view schematically showing one step following the one step of FIG. 15C. FIG. 16 is a cross-sectional view schematically showing an example of an apparatus that can be used in the manufacturing method of the present embodiment. FIG. 17A is a cross-sectional view schematically showing the shape of the sample 1 used in the first embodiment. FIG. 17B is a cross-sectional view schematically showing the shape of the sample 2 used in the first embodiment. FIG. 17C is a cross-sectional view schematically showing the shape of the sample 3 used in the first embodiment. FIG. 18 is a diagram schematically showing a three-point bending test simulated in an example. FIG. 19A is a graph schematically showing an example of the amount of energy absorbed by each sample in the simulation of Example 1. FIG. 19B is a graph schematically showing another example of the energy absorption amount of each sample in the simulation of Example 1. FIG. 20A is a graph schematically showing an example of the amount of energy absorbed by each sample in the simulation of Example 2. FIG. 20B is a graph schematically showing another example of the energy absorption amount of each sample in the simulation of Example 2. It is sectional drawing which shows typically an example of the deformation of the sample in the test of Example 1. FIG. It is sectional drawing which shows typically an example of the deformation of the sample in the test of Example 2. FIG.

As a result of diligent studies, the inventor of the present application has newly found that a specific structure improves the property against collision. Furthermore, the inventor of the present application has found that the degree of freedom in the method of connecting the constituent members can be increased by using the structure. The present invention is based on these new findings.

Hereinafter, embodiments of the present invention will be described. In the following description, embodiments of the present invention will be described with examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present invention can be obtained.

(Structural members for automobiles)
The structural member of the present embodiment is a structural member for automobiles. This structural member includes a press-molded product formed of a single steel plate and a metal member made of a metal plate fixed to the press-molded product. The press-molded product may be referred to as a "press-molded product (P)" below, and the metal member may be referred to as a "metal member (S1)". The press-molded product (P) includes a superposed portion. The metal member (S1) is fixed to the overlapping portion.

The metal member (S1) may be fixed to the entire overlapping portion, or may be fixed to only a part of the overlapping portion. The metal member (S1) is usually a press-molded product formed by press molding, but may be other than that.

Examples of the metal member (S1) include a steel plate, an aluminum plate, a titanium plate, a magnesium plate, and the like. The metal member (S1) is typically a steel plate, and may be a steel plate of the same type as the steel plate constituting the press-molded product (P). Unless otherwise specified, the metal member (S1) in the present specification can be replaced with a steel plate member. A member made of resin or CFRP may be used instead of the metal member (S1). The metal member (S1) may be a flat metal plate or a molded metal plate.

(Press molded product (P))
The press-molded product (P) will be described below. The press-molded product (P) is a press-molded product formed of a single steel plate. The press-molded product (P) is formed from at least one of the two vertical wall portions, the top plate portion connecting the two vertical wall portions, and the two boundary portions connecting the vertical wall portion and the top plate portion. Includes a protruding portion. In the protruding portion, a steel plate extending from the vertical wall portion (steel plate continuing from the vertical wall portion) and a steel plate extending from the top plate portion (steel plate continuing from the top plate portion) are overlapped at at least at the tip of the protruding portion. It protrudes from the boundary. The angle formed by the top plate portion and the overlapping portion may be referred to as "angle X" below. The details of the angle X will be described in the first embodiment.

At least at the tip of the protruding portion, the steel plate extending from the top plate portion and the steel plate extending from the vertical wall portion are overlapped to form a double layer. In this specification, the portion where the steel plates are doubly overlapped in the protruding portion is referred to as a "superimposed portion". The overlapped portion has a plate-like shape as a whole. A steel plate is bent at the tip of the protrusion.

The length of the protruding portion and the length protruding from the boundary portion may be referred to as "length D" below. The length D is the length of the protrusion in the cross section perpendicular to the longitudinal direction. The length of the overlapped portion in the cross section perpendicular to the longitudinal direction is not more than 1 times the length D of the protruding portion, and is in the range of 0.1 to 1 times (for example, the range of 0.5 to 1 times, or 0. It may be in the range of 3 to 0.8 times). As the length D, a length to which the metal member (S1) can be fixed is selected.

The press-formed product (P) can be formed by deforming one steel plate (material steel plate). Specifically, the press-molded product (P) can be manufactured by press-molding one material steel sheet by the manufacturing method of the present invention. The material steel sheet used as the material will be described later.

The press-molded product (P) has an elongated shape as a whole. The vertical wall portion, the top plate portion, the flange portion, and the protruding portion all extend along the longitudinal direction of the press-molded product. The protrusion may be formed over the entire longitudinal direction of the press-molded product, or may be formed only in a part of the press-molded product in the longitudinal direction.

In the following, the area surrounded by the two vertical wall portions and the top plate portion is referred to as "the inside of the press-molded product (P)", and the region opposite to the inside of the vertical wall portion and the top plate portion. May be referred to as "outside of the press-molded product (P)".

The top plate connects the two vertical walls. More specifically, the top plate portion connects the two vertical wall portions via the protrusions. From another point of view, the top plate portion is a horizontal wall portion connecting two vertical wall portions. Therefore, in this specification, the top plate portion can be read as the lateral wall portion. When the press-molded product (P) is arranged with the side wall portion (top plate portion) facing downward, the side wall portion can also be referred to as a bottom plate portion. However, in this specification, the side wall portion is referred to as a top plate portion based on the case where the side wall portion is arranged above.

The angle Y formed by the top plate portion and the vertical wall portion is usually 90 ° or its vicinity. The angle Y will be described in the first embodiment. The angle Y may be less than 90 °, but is usually 90 ° or more, and may be in the range of 90 ° to 150 °. The two angles Y may be different, but are preferably substantially the same (the difference between the two is within 10 °), and may be the same.

The press-molded product (P) may include two protrusions protruding from each of the two boundaries. In this case, one protrusion protrudes from each of the two boundary portions. The angles X at the two protrusions may be substantially the same (the difference between the two is within 10 °) or may be different. A different metal member (S1) may be fixed to each of the overlapping portions of the two protruding portions. Alternatively, one metal member (S1) may be fixed to the overlapping portion of the two protruding portions. Alternatively, the metal member (S1) may be fixed to only one of the overlapping portions of the two protruding portions.

The angle X formed by the top plate portion and the overlapping portion may be in the range of 80 ° to 180 ° (for example, in the range of 90 ° to 180 °) or in any other range. The angle X may be in the range of 90 ° to 135 ° or may be in the range of 135 ° to 180 °.

The metal member (S1) may be fixed to the press-molded product (P) at either one of the vertical wall portion and the top plate portion and at two locations of the overlapping portion. In that case, the angle formed by at least one of the overlapped portions may be in the range of 90 ° to 175 ° (for example, the range of 90 ° to 135 °). According to this configuration, as will be described later, the reliability of fixing the press-molded product (P) and the metal member (S1) can be improved. This configuration is preferably applied when the metal member (S1) is fixed to the press-molded product (P) by welding. When fixing at two places, the fixing methods at the two places may be the same or different.

As long as the effect of the present invention can be obtained, there is no limitation on the method of fixing the press-molded product (P) and the metal member (S1). The method for fixing the press-molded product (P) and the metal member (S1) is preferably selected according to the material of the metal member (S1). The press-molded product (P) and the metal member (S1) may be fixed by at least one selected from the group consisting of welding, adhesive, brazing, rivets, and friction stir welding. Examples of welding include resistance spot welding and laser welding. In the structural member of the present embodiment, the metal member (S1) is fixed to the superposed portion of the press-molded product (P). Therefore, both can be fixed by using various fixing methods. Friction stir welding is preferable in that the temperature rise of the material can be suppressed.

The press-molded product (P) and the metal member (S1) may be fixed by resistance spot welding in which electrodes are applied to both sides of the fixing portion to perform welding. The welding method may be referred to as "both sides spot welding" in this specification. As described in the first embodiment, by using the press-molded product (P) having the overlapped portion, fixing using spot welding on both sides can be easily performed. Double-sided spot welding is preferred in terms of cost and reliability.

In the press-molded product (P), the steel plate extending from the vertical wall portion and the steel plate extending from the top plate portion may be fixed at the protruding portion. For example, the steel plate that is doubled in the overlapped portion may be fixed by the method exemplified as the fixing method between the press-formed product (P) and the metal member (S1). Further, even if the steel plate extending from the vertical wall portion and the steel plate extending from the top plate portion are arc-welded (fillet welded) at the base of the protruding portion (the boundary between the top plate portion and the vertical wall portion and the protruding portion). Good. The steel plate extending from the vertical wall portion and the steel plate extending from the top plate portion may be fixed before the metal member (S1) is fixed to the overlapping portion, or the metal member (S1) may be fixed to the overlapping portion. You may do it at the same time. For example, as a method of fixing the metal member (S1) to the overlapping portion, when a method of fixing the steel plate and the metal member (S1) that are doubled at the overlapping portion together is adopted, they are fixed. It may be fixed at once. Examples of such methods include resistance spot welding and laser welding.

The press-molded product (P) may include two flange portions extending from the ends of the two vertical wall portions (the end opposite to the end on the top plate side).

The structural member of the present embodiment may further include another member made of a metal plate (for example, a steel plate). The other member may be referred to as a "member (S2)" below. As the metal plate constituting the member (S2), those exemplified as the metal plate constituting the metal member (S1) can be used. The metal plate constituting the member (S2) is typically a steel plate, and a steel plate of the same type as the steel plate constituting the press-formed product (P) may be used. The member (S2) is fixed to the press-molded product (P). Even if the member (S2) is fixed to the two flange portions so that the press-molded product (P) and the member (S2) form a closed cross section (a hollow body from another viewpoint; the same applies hereinafter). Good. The member (S2) may be fixed to the entire flange portion of the press-molded product (P), or may be fixed to only a part of the flange portion. The member (S2) may be a flat metal plate (back plate) or a press-molded product formed by press molding. For example, the member (S2) may be the press-molded product (P) of the present invention. In that case, the two press-molded products (P) may be fixed to each other so as to form a closed cross section.

The method for fixing the press-molded product (P) and the member (S2) is not limited, and the method exemplified as the method for fixing the press-molded product (P) and the metal member (S1) may be applied. For example, the press-molded product (P) and the member (S2) may be fixed by resistance spot welding.

The tensile strength of the steel sheet constituting the press-molded product (P) may be 490 MPa or more (for example, 590 MPa or more, 780 MPa or more, 980 MPa or more, or 1200 MPa or more). The upper limit of the tensile strength is not limited and may be 2000 MPa or less. When the second step of the manufacturing method described later is performed by hot stamping, the tensile strength of the press-molded product can be made higher than the tensile strength of the steel plate (blank) which is the material. When the metal member (S1) and the member (S2) are made of a steel plate, the tensile strength of the steel plate constituting the metal member (S1) and the member (S2) is exemplified with respect to the tensile strength of the steel plate of the press-formed product (P). It is preferable that it is in the above range.

The press-molded product (P) and the structural member of the present embodiment including the press-molded product (P) can be used as a structural member of an automobile. Examples of press molded product (P) applications include side sills, pillars (front pillars, front pillar lowers, center pillars, etc.), roof rails, roof arches, bumpers, belt line reinforcements, and door impact beams. Structural members other than these may be used. The structural members of the present embodiment can be used for structural members of transportation means (vehicles, ships, aircraft, etc.) other than automobiles. For example, it is possible to use the structural members of the present embodiment as structural members of various vehicles (automobiles, motorcycles, railroad vehicles, etc.).

The press-molded product (P) may be a press-molded product that constitutes a portion connected below the A pillar. In this case, the press-molded product (P) may include an A pillar. The member constituting the portion connected below the A-pillar is sometimes called the A-pillar lower. In this case, the metal member (S1) may be a member constituting the upper member. Such members are sometimes referred to as upper member rears.

The press-molded product (P) may be a side sill inner. Side sill inners are sometimes called rocker inners. In this case, the metal member (S1) may be a floor panel.

(Manufacturing method of structural members)
The method of this embodiment for manufacturing a structural member for an automobile will be described below. This manufacturing method is a method for manufacturing the structural member of the present embodiment. Therefore, since the matters described for the structural members of the present embodiment can be applied to the manufacturing method of the present embodiment, duplicate description may be omitted. In addition, the matters described about the manufacturing method of the present embodiment can be applied to the structural members of the present embodiment.

The manufacturing method of the present embodiment includes a first step, a second step, and a third step in this order. In the first step, a preformed product including two vertical wall portions and a top plate portion is formed by deforming the material steel plate. In the second step, the press-molded product (P) is formed by press-molding the pre-molded product. In the third step, the metal member (S1) is fixed to the overlapped portion of the press-molded product (P). The premolded article includes a surplus portion for forming a protruding portion. In the second step, the overlapped portion is formed by superimposing at least a part of the material steel plate (deformed material steel plate) constituting the surplus portion. Typically, in a premolded article, there is no clear boundary between the surplus and the rest, but there may be some boundary between them.

The first step is not particularly limited, and may be performed by a known press molding. The second step will be described later. The press-molded product (P) obtained in the second step may be further post-treated.

In the following, a steel plate (material steel plate) as a starting material may be referred to as a “blank”. The blank is usually a flat steel plate and has a planar shape corresponding to the shape of the press-molded product (P) to be formed. The thickness and physical properties of the blank are selected according to the properties required for the press-molded product. The thickness of the blank may be in the range of, for example, 0.4 mm to 4.0 mm, or may be in the range of 0.8 mm to 2.0 mm. The wall thickness of the press-molded product (P) is determined by the thickness of the blank and the processing process, and may be in the range of the thickness of the blank exemplified here.

The blank is preferably a high-tensile steel plate having a tensile strength of 490 MPa or more (for example, 590 MPa or more, 780 MPa or more, 980 MPa or more, or 1200 MPa or more). In order to reduce the weight of the structural member, the tensile strength of the blank is preferably high, and more preferably 590 MPa or more (for example, 980 MPa or more, or 1180 MPa or more). The upper limit of the tensile strength of the blank is not limited, and in one example, it is 2000 MPa or less. The tensile strength of the press-molded product (P) is usually equal to or higher than the tensile strength of the blank, and may be in the range illustrated here. When the metal member (S1) and the metal plate constituting the member (S2) are steel plates, the thickness and tensile strength of the steel plates can also be selected from the above-exemplified range.

When the tensile strength of the material steel sheet (blank) is 590 MPa or more, the second step may be performed by hot stamping (hot stamping). When the tensile strength of the blank is high, cracks are likely to occur at the tip of the protruding portion in the cold press. Therefore, when a blank having a tensile strength of 590 MPa or more (for example, 780 MPa or more) is used, it is preferable to perform the second step by hot stamping. Of course, even when a blank having a tensile strength of less than 590 MPa is used, the second step may be performed by hot stamping. When performing hot stamping, a blank having a known composition suitable for the hot stamping may be used.

When the tensile strength of the blank is 590 MPa or more and the wall thickness is 1.4 mm or more, it is particularly preferable to perform the second step by hot stamping in order to prevent cracking at the protruding portion. For the same reason, when the tensile strength of the blank is 780 MPa or more and the wall thickness is 0.8 mm or more, it is particularly preferable to perform the second step by hot stamping. Since the heated steel sheet has high ductility, when the second step is performed by hot stamping, cracking is unlikely to occur even if the wall thickness of the blank is 3.2 mm.

When the tensile strength of the blank is high, cracks are likely to occur at the tip of the protruding portion in the cold press. Therefore, when the tensile strength of the formed steel sheet is 1200 MPa or more (for example, 1500 MPa or more or 1800 MPa or more), it is preferable to perform the second step by hot stamping. Of course, even when the tensile strength of the formed steel sheet is less than 1200 MPa, the second step may be performed by hot stamping. In particular, when a blank having high tensile strength is used, it is preferable to perform the second step by hot stamping.

The deformation in the first step is usually not very large. Therefore, regardless of the tensile strength of the blank, the first step can usually be performed by cold working (for example, cold pressing). However, if necessary, the first step may be performed by hot working (for example, hot pressing). In a preferred example, the first step is cold working and the second step is hot stamping.

An example of hot stamping will be described below. When performing hot stamping, first, the work piece (blank or premolded product) is heated to a predetermined quenching temperature. The quenching temperature is higher than the A3 transformation point (more specifically, the Ac3 transformation point) at which the workpiece is austenitized, and may be, for example, 910 ° C. or higher. Next, the heated workpiece is pressed with a pressing device. Since the work piece is heated, it is unlikely to crack even if it is greatly deformed. Quench the work piece when pressing the work piece. Due to this quenching, the workpiece is hardened during press working. Quenching of the work piece can be carried out by cooling the mold or by ejecting water from the mold toward the work piece. The hot stamping procedure (heating and pressing, etc.) and the equipment used therein are not particularly limited, and known procedures and equipment may be used.

The premolded article may include a U-shaped portion having a U-shaped cross section perpendicular to the longitudinal direction. The U-shaped portion serves as two vertical wall portions, a top plate portion, and a protruding portion. Normally, a portion to be a flange portion is connected to the end portion of the U-shaped portion. In the following description, the term "cross section" basically means a cross section in the direction perpendicular to the longitudinal direction.

In the production method of the present invention, the second step may include the following steps (a) and (b). In the step (a), the portion of the premolded product that becomes the top plate portion is pressed by a pair of press dies. In the step (b), a portion of the premolded product to be a vertical wall portion is pressed by at least one of a pair of press molds and a cam mold. In the production method of the present invention, a mold may be used in which a protrusion is formed when both the step (a) and the step (b) are completed. The cam type mainly moves in a direction perpendicular to the pressing direction (horizontal direction). In a typical example, the cam type moves only horizontally.

The timing of performing the steps (a) and (b) can be selected depending on the situation, and either one may be completed first, or both may be completed at the same time. Further, either step (a) or step (b) may be started first, or both may be started at the same time. The first to third examples in which the timing of completion of the step (a) and the step (b) are different will be described below.

In the first example of the second step, the step (b) is completed after the step (a) is completed. The first example is preferably performed when the angle X formed by the top plate portion and the overlapping portion is 135 ° or less (for example, in the range of 90 ° to 135 °). As long as the step (b) is completed after the step (a) is completed, the cam type movement in the step (b) may be started before the step (a) is completed.

In the second example of the second step, the step (a) is completed after the step (b) is completed. The second example is preferably performed when the angle X formed by the top plate portion and the overlapping portion is 135 ° or more (for example, in the range of 135 ° to 180 °). As long as the step (a) is completed after the step (b) is completed, the movement of the pair of press molds in the step (a) may be started before the step (b) is completed.

In the third example of the second step, step (a) and step (b) are completed at the same time. As long as the step (a) and the step (b) are completed at the same time, there is no limitation on the movement start time of the pair of press molds in the step (a) and the movement start time of the cam mold in the step (b).

In the manufacturing method of the present invention, a through hole may be formed in a portion of the premolded product to be the top plate portion. Then, in the second step, the movement of the portion to be the top plate portion may be suppressed by passing the pins protruding from the pair of press molds through the through holes. The pin usually projects from one of a pair of press molds. A through hole through which a pin passes is formed on the other side of the pair of press molds. Through holes are generally formed at the blank stage, but may be formed at other stages prior to the second step.

In the third step, the metal member (S1) is fixed to the overlapped portion of the press-molded product (P). Examples of fixing methods include the methods described above. By the third step, the structural member of this embodiment is obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are exemplary, and at least a portion of the configurations of the following embodiments can be replaced with the configurations described above. In the following description, the same parts may be designated by the same reference numerals and duplicate description may be omitted.

In the drawings below, a gap may be shown between the steel plates that are overlapped at the overlapped portion for ease of understanding, but usually the steel plates that are overlapped at the overlapped portion are in close contact with each other. There is. Further, in the following, a case where a protruding portion (overlapping portion) is provided at each of the two boundary portions may be illustrated, but only one of the two boundary portions has a protruding portion (overlapping portion). It may be provided.

(First Embodiment)
In the first embodiment, an example of the structural member of the present invention will be described. A perspective view of the structural member 400 of the first embodiment is schematically shown in FIG. Further, a cross-sectional view perpendicular to the longitudinal direction of the structural member 400 is schematically shown in FIG. In the following, the upper portion (top plate portion side) in FIG. 2 may be referred to as the upper portion of the press-molded product 100, and the lower portion (flange portion side) in FIG. 2 may be referred to as the lower portion of the press-molded product 100.

The structural member 400 includes a press-molded product 100 which is a press-molded product (P) and a metal member (steel plate member) 410 which is a metal member (S1). 1 and 2 show an example in which the metal member 410 is fixed to a part of the overlapped portion 115d of the press-molded product 100 in the longitudinal direction.

The press-molded product 100 is made of one steel plate 101. With reference to FIGS. 1 and 2, the press-molded article 100 includes two vertical wall portions 111, a top plate portion 112, two flange portions 113, and two projecting portions 115. The vertical wall portion 111, the top plate portion 112, and the flange portion 113 are flat plates, respectively. The top plate portion 112 connects the two vertical wall portions 111 via the two protruding portions 115. In the example shown in FIG. 2, the two flange portions 113 extend substantially horizontally from the lower end portions of the two vertical wall portions 111 toward the outside. That is, the flange portion 113 is substantially parallel to the top plate portion 112.

The projecting portion 115 projects outward from the boundary portion (corner portion) 114 connecting the vertical wall portion 111 and the top plate portion 112. The overlapping portion 115d exists at least on the tip portion 115t side of the protruding portion 115. In the overlapping portion 115d, the steel plate 101a extending from the top plate portion 112 and the steel plate 101b extending from the vertical wall portion 111 are overlapped and brought into close contact with each other. The steel plate 101a and the steel plate 101b are each a part of the steel plate 101. The steel plate (steel plate 101a) extending from the top plate portion 112 is bent in the opposite direction at the tip portion 115t to form the steel plate 101b. The overlapping portion 115d has a flat plate shape as a whole. The cross section (cross section perpendicular to the longitudinal direction) of the press-molded product 100 excluding the protruding portion 115 is substantially hat-shaped.

As shown in FIG. 2, the angle formed by the top plate portion 112 and the overlapping portion 115d is defined as an angle X. More specifically, the angle X refers to the angle formed by the surface including the outer surface 112s of the top plate portion 112 and the surface including the surface 115ds of the overlapping portion 115d (the surface of the steel plate 101a in the overlapping portion 115d). 1 and 2 show a case where the angle X is 180 °. In this case, the top plate portion 112 and the overlapping portion 115d are parallel to each other. In a preferable example when the angle X is 180 °, there is no step between the steel plate 101a extending from the top plate portion 112 and the top plate portion 112. From another point of view, the state where the angle X is 180 ° can be regarded as the state where the angle formed by the top plate portion 112 and the overlapping portion 115d is 0 °.

The angle X may be in the range described above. FIG. 3 shows a cross-sectional view of an example when the angle X is 145 °.

When the angle X is larger than 90 °, when the press-molded product 100 is viewed from above the top plate portion 112, the steel plate 101b constituting the protruding portion 115 is obscured by the steel plate 101a. Such a portion is sometimes called a negative angle portion. From another point of view, the negative angle portion is a portion having a reverse gradient when press molding is performed only with the upper mold and the lower mold.

The length D of the protruding portion 115 and protruding from the boundary portion 114 (see FIG. 17A) may be in the above-mentioned range. When the steel plate is curved at the boundary portion 114, the length at which the protruding portion 115 protrudes from the position assuming that there is no curve is defined as the length D. Specifically, the position where the surface including the vertical wall portion 111 and the surface including the top plate portion 112 intersect is regarded as a boundary portion, and the length protruding from that position is defined as the length D.

The overlapping portion 115d is not rounded into a tubular shape. Therefore, the protruding portion 115 is different from the reinforcing portion rounded into a tubular shape described in FIG. 6 of Patent Document 4. Further, in the overlapped portion 115d, the two steel plates are in close contact with each other. Further, in the region other than the tip portion 115t, a part of the steel plate constituting the protruding portion 115 is curved but not bent. That is, except for the tip portion 115t, the protruding portion 115 does not have a ridge line portion that protrudes toward the outside of the protruding portion 115. In these respects, the press-molded product 100 is different from the parts described in Patent Document 3.

FIG. 2 shows an example in which the angle Y formed by the vertical wall portion 111 and the top plate portion 112 is larger than 90 °. Here, the angle Y is the angle shown in FIG. 2, that is, the angle formed by the vertical wall portion 111 and the top plate portion 112 inside the press-molded product 100.

As shown in FIG. 2, the corner portion 116 connecting the vertical wall portion 111 and the flange portion 113 preferably has a rounded shape. Since the corner portion 116 has a rounded shape, buckling at the corner portion 116 can be suppressed.

The corner portion of the boundary between the steel plate 101b of the projecting portion 115 and the vertical wall portion 111 is preferably a curved surface. By making the corner portion a curved surface, buckling at the corner portion can be suppressed. The radius of curvature of the corner in the direction perpendicular to the longitudinal direction is in the range of 0.1 to 1 times the length D (for example, in the range of 0.2 to 0.8 times or 0.2 to 0.5 times). It may be in the range). When the angle X is smaller than 180 °, the corner portion of the boundary between the steel plate 101a of the protruding portion 115 and the vertical wall portion 111 may be a curved surface.

It is not necessary that the protrusion is formed over the entire length of the press-molded product. FIG. 4 schematically shows a perspective view of a press-molded product in which a protrusion is formed only in a part in the longitudinal direction. In the press-molded product 100 of FIG. 4, the projecting portions 115 are not formed in the regions P2 at both ends in the longitudinal direction, and the projecting portions 115 are formed in the central region P1 in the longitudinal direction.

The steel plates that are doubly stacked by the protrusion 115 may be fixed to each other. As the fixing method, the method exemplified as the fixing method between the press-molded product (P) and the metal member (S1) may be used. For example, the area A and / or the area B shown in FIG. 5 may be welded. There is no limitation on the welding method. Welding of the region A that is not the end of the protrusion may be performed by resistance spot welding or laser welding. Welding (fillet welding) of the region B at the boundary between the protrusion 115 and the other portion may be performed by arc welding.

Although the case where the angle X is 180 ° is shown in FIGS. 1 and 2, the angle X may be in the above-mentioned range. FIG. 6 shows an example of the press-molded product 100 when the angle X is 90 °. Further, a cross-sectional view perpendicular to the longitudinal direction of the press-molded article 100 of FIG. 6 is schematically shown in FIG. Since the meanings of the reference numerals in FIGS. 6 and 7 have been described above, description thereof will be omitted. A metal member 410 is fixed to the overlapping portion 115d of the press-molded product 100 shown in FIGS. 6 and 7.

Examples of the case where the structural member of the present embodiment includes another member (S2) made of a steel plate are shown in FIGS. 8A to 8C. 8A to 8C are views schematically showing a cross section perpendicular to the longitudinal direction of the structural member. In FIGS. 8A to 8C, the press-molded product 100 and the member (S2) are shown, and the metal member 410 (metal member (S1)) is not shown. As described above, the metal member 410 is fixed to the overlapping portion of the press-molded product 100.

In the examples shown in FIGS. 8A to 8C, the press-molded product 100 and the member 201 form a closed cross section. In the example shown in FIG. 8A, a member (back plate) 201 made of a steel plate is fixed to the press-molded product 100. The member 201 is welded to the two flange portions 113 of the press-molded product 100. In the example shown in FIG. 8B, another press-molded product 202 is fixed to the press-molded product 100. The press-molded product 202 has a substantially hat-shaped cross section. The press-molded product 100 and the press-molded product 202 are arranged so that their inner regions face each other, and the flange portion 113 of the press-molded product 100 and the flange portion 202a of the press-molded product 202 are welded to each other. In the example shown in FIG. 8C, the two press-molded products 100 are arranged so that their inner regions face each other, and the flange portions 113 of each other are welded to each other. One of the two press-molded products 100 can be regarded as a member (S2). Further, the member 201 and the press-molded product 202 are members (S2). 8A to 8C have described a case where a press-molded product having the same shape as the press-molded product 100 shown in FIG. 1 is used, but other press-molded products may be used.

FIG. 9A schematically shows an example of a structural member in the case where the press-molded product (P) is a press-molded product constituting a portion connected below the A pillar and the metal member (S1) is a member constituting the upper member. Shown. Further, a cross-sectional view taken along the line IXB-IXB of FIG. 9A is schematically shown in FIG. 9B.

In the structural member 400a shown in FIGS. 9A and 9B, the press-molded product 100a is a press-molded product constituting a portion connected below the A pillar. A member 201a, which is a member (S2), is fixed to the flange portion of the press-molded product 100a so as to form a closed cross section. The metal member 410a is a member constituting the upper member. The metal member 410a is fixed to the overlapping portion 115d in the fixing portion 420. When resistance spot welding is used, the fixed portion 420 is a nugget.

In the assembly of automobiles, a member (S2) is often welded to a press-molded product (P) to form a closed cross-section member (hollow body), and then a metal member (S1) is welded. In the conventional press-molded product having no overlapping portion, it is necessary to weld the metal member 410 to the top plate portion 112. In that case, it is difficult to weld the metal member 410 to the top plate portion 112 by spot welding on both sides after welding the member 201. This is always a problem when performing spot welding on both sides of a long closed cross-section member (such as a tubular body). On the other hand, the press-molded product 100 has a superposed portion 115d. Therefore, as shown in FIG. 9C, even after the member 201 is welded to the press-molded product 100 to form a hollow body, two electrodes (electrode rods) 51a and 51b are placed on the welded portion from both sides of the welded portion. It can be reached and spot welding on both sides can be easily performed. Further, it is easy to apply not only to spot welding on both sides but also to other fixing methods. Therefore, by using the press-molded product 100, the degree of freedom for fixing the metal member 410 to the press-molded product 100 is remarkably increased.

FIG. 10 schematically shows a perspective view of an example of a structural member when the press-molded product (P) is a side sill inner and the metal member (S1) is a floor panel. Note that FIG. 10 shows only a part of the floor panel.

In the structural member 400b of FIG. 10, the press-molded product 100b is a side sill inner, and the metal member 410b is a floor panel. The metal member 410b is fixed to the overlapping portion of the press-molded product 100b.

(Second Embodiment)
As described above, the metal member (S1) may be fixed to the press-molded product at either one of the vertical wall portion and the top plate portion and at two locations of the overlapping portion. In the second embodiment, an example of such a structural member will be described. It is possible to apply the configuration of the second embodiment to the structural members described in the first embodiment.

A cross-sectional view of an example of the structural member of the second embodiment is schematically shown in FIG. 11A, and a cross-sectional view of another example is schematically shown in FIG. 11B. In the structural member 400 shown in FIGS. 11A and 11B, the metal member 410 is fixed to the press-molded product 100 at two points, the fixing portion 420a and the fixing portion 420b. In the structural member of FIG. 11A, the fixing portion 420a is formed on the top plate portion 112, and the fixing portion 420b is formed on the overlapping portion 115d. In this case, the angle formed by the portion where the fixed portion 420a is formed (top plate portion 112) and the portion where the fixed portion 420b is formed (overlapping portion 115d) is the above-mentioned angle X.

In the structural member 400 of FIG. 11B, the fixing portion 420a is formed on the vertical wall portion 111, and the fixing portion 420b is formed on the overlapping portion 115d. In this case, the angle formed by the portion where the fixed portion 420a is formed (vertical wall portion 111) and the portion where the fixed portion 420b is formed (overlapping portion 115d) can be determined by using the angles X and Y described above. It is represented by (360-XY) degrees.

The angle formed by the portion where the fixed portion 420a is formed (vertical wall portion 111 or the top plate portion 112) and the portion where the fixed portion 420a is formed (overlapping portion 115d) is other than 180 ° (for example, described above). By setting the range), the reliability of the fixed portion can be improved.

The fracture mode of the spot welded joint is roughly divided into a tensile shear (TSS) mode, an L-shaped joint (LTS) mode, and a cross joint (CTS) mode. In general, the strength of the joint is highest in TSS and decreases in the order of LTS and CTS. However, it is difficult to control the fracture mode with a general spot welded joint because forces are applied from various directions at the time of collision.

12A and 12B, respectively, show the case where the press-molded product 100 and the metal member 410 are subjected to a pulling force in the direction of the arrow for the structural member shown in FIG. 11A. In either case of FIGS. 12A and 12B, the breaking mode of at least one of the fixing portions 420a and 420b is the TSS mode. Therefore, according to the structural member of the second embodiment, higher joint strength can be obtained, and as a result, high collision safety can be realized.

(Third Embodiment)
In the third embodiment, a method for manufacturing the structural member of the present embodiment will be described. In the third embodiment, an example of producing the press-molded product described in the first and second embodiments will be described, but other press-molded products of the present invention can also be produced in the same manner. In the third embodiment, an example in which the second step is performed by hot stamping will be described.

First, in the first step, the preformed product 301 including the portion serving as the two vertical wall portions 111 and the portion serving as the top plate portion 112 is formed by deforming the material steel plate. The first step can be performed by the method described above (for example, press working). A cross section (cross section perpendicular to the longitudinal direction) of an example of the preformed product 301 formed in the first step is schematically shown in FIG.

The premolded product 301 includes a U-shaped portion 301a and a flat portion 301b that serves as a flange portion 113. The U-shaped portion 301a includes two vertical wall portions 111 and a portion serving as a top plate portion 112, and further includes a portion serving as a protruding portion 115 (surplus portion 301ae). The cross section of the preformed product 301 is substantially hat-shaped. The cross section of the U-shaped portion 301a is substantially U-shaped (upside down in FIG. 13).

Let the length (cross-sectional length) of the U-shaped portion 301a be Lu. Further, in the press-molded product, the height of the vertical wall portion is Hb (corresponding to Hb1 in FIG. 11A), and the width between the two vertical wall portions is Wb (corresponding to Wb1 in FIG. 11A). The U-shaped portion 301a includes a surplus portion 301ae that becomes a protruding portion 115 in the second step, in addition to a portion that becomes the vertical wall portion 111 and a portion that becomes the top plate portion 112. Therefore, the length Lu, the width Wb, and the height Hb satisfy the relationship of Wb + 2Hb <Lu. Further, the width of the U-shaped portion 301a is Wa, and the height is Ha. Usually, the relationship of Wb ≦ Wa and the relationship of Wb + 2Hb <Wa + 2Ha are satisfied. In the U-shaped portion 301a of the premolded product 301 shown in FIG. 13, there is no clear boundary between the surplus portion 301ae and the other portion.

The end portion of the flat portion 301b of the premolded product 301 may be lowered downward (in the direction away from the top plate portion 112). In FIGS. 14A to 14D below, an example in which the second step is performed using the preformed product 301 in which the end portion of the flat portion 301b is not lowered will be described. As shown in FIGS. 15A to 15D, the premolded product 301 in which the end portion of the flat portion 301b is lowered can also be molded in the same manner.

The second step is performed by hot stamping. First, the preformed product 301 is heated to a temperature equal to or higher than the Ac3 transformation point (for example, a temperature higher than the Ac3 transformation point by 80 ° C. or higher). This heating is performed, for example, by heating the premolded product 301 in a heating device.

Next, the heated preformed product 301 is pressed by a pressing device. An example of the structure of the press mold used for press working is shown in FIG. 14A. The press device includes a pair of press molds 10, a plate 13, a telescopic mechanism 14, a cam pressing mold 15, and a cam mold (sliding mold) 21. The pair of press dies 10 includes an upper die 11 and a lower die 12. The lower mold 12 includes a convex portion 12a. The cam pressing type 15 and the cam type 21 have inclined surfaces 15a and 21a acting as a cam mechanism, respectively. The cam pressing mold 15 is fixed to the plate 13 via a telescopic mechanism 14 that can be expanded and contracted. As the expansion / contraction mechanism, a known expansion / contraction mechanism such as a spring or a hydraulic cylinder can be used.

As the plate 13 is lowered, the upper die 11 and the cam pressing die 15 are lowered. As the cam pressing die 15 descends, the cam die 21 is pushed by the cam pressing die 15 and moves to the convex portion 12a side of the lower die 12. As is well known, the timing of movement of the cam mold 21 can be adjusted by changing the positions and shapes of the inclined surfaces 15a and 21a. That is, by these adjustments, the timing of the completion of the above-mentioned step (a) and the completion of the step (b) can be adjusted. The cam mold 21 may be moved by a hydraulic cylinder or the like without using the cam mechanism.

In this embodiment, an example is illustrated in which the upper die 11 and the cam pressing die 15 are attached to the same slide of the press machine via the plate 13. However, the upper die 11 and the cam pressing die 15 may be attached to separate slides of the press and operated individually. Further, in this embodiment, an example in which the cam mold 21 is moved by being pressed against the cam pressing mold 15 is illustrated. However, the cam mold 21 may be moved by a drive device directly attached to the cam mold 21.

The press mold 10 and the cam mold 21 can be cooled. For example, the press mold 10 and the cam mold 21 may be configured such that cooling water circulates inside them. By performing the press using the cooled mold, the heated premolded article 301 is molded and cooled. As a result, press molding and quenching are performed. Cooling may be performed by ejecting water from the mold.

An example of a step of press molding using the apparatus of FIG. 14A will be described. 14A to 14D schematically show an example in which the second step is performed by the method of the second example described above. The method of this second example is preferably used when the angle X is 135 ° or more (for example, in the range of 135 ° to 180 °).

First, as shown in FIG. 14A, the premolded product 301 is arranged between the upper mold 11 and the lower mold 12. Next, the plate 13 is lowered. The cam mold 21 is pushed by the cam pressing mold 15 that descends with the plate 13, and slides toward the convex portion 12a. As a result, as shown in FIG. 14B, the lower mold 12 (convex portion 12a) and the cam mold 21 press and restrain the portion to be the vertical wall portion 111. In this way, step (b) is completed.

Next, as shown in FIG. 14C, the plate 13 is further lowered, whereby the pressing of the portion to be the top plate portion is started. At this time, the expansion / contraction mechanism 14 contracts. Since the premolded product 301 has a surplus portion, the surplus portion projects toward the cam mold 21 side.

Next, as shown in FIG. 14D, the upper die 11 is lowered to the bottom dead center, and the portion to be the top plate portion is pressed and restrained by the upper die 11 and the lower die 12 (convex portion 12a). In this way, step (a) is completed. As described above, press molding is completed. The surplus portion is folded between the upper mold 11 and the cam mold 21 to form a protruding portion 115 having a superposed portion 115d. In this way, the press-molded product 100 is obtained.

Next, an example in which the second step is performed by the method of the first example described above will be described. 15A to 15D schematically show each step. The method of this first example is preferably used when the angle X is 135 ° or less (for example, in the range of 90 ° to 135 °).

15A to 15D show a case where the end portion of the flat portion 301b (see FIG. 13) to be the flange portion 113 is bent downward and the lower mold 12 has a corresponding shape. According to such a configuration, the end portion of the flat portion 301b can be easily inserted between the lower surface of the cam mold 21 and the lower mold 12. Of course, as shown in FIGS. 14A to 14D, the end portion of the flat portion 301b does not have to be bent downward. That is, in the manufacturing method of the present invention, the end portion of the preformed part to be the flange portion may or may not be bent downward. When the end portion of the portion to be the flange portion is bent downward, the corresponding recess may be formed in the lower mold.

In the device shown in FIG. 15A, the upper die 11 is fixed to the plate 13 via the telescopic mechanism 14. On the other hand, the cam pressing type 15 is fixed to the plate 13 without going through the expansion / contraction mechanism 14.

In this second step, first, as shown in FIG. 15A, the preformed product 301 is arranged between the upper mold 11 and the lower mold 12. Next, as shown in FIG. 15B, the plate 13 is lowered, and the portion to be the top plate portion is pressed and restrained by the upper mold 11 and the lower mold 12 (convex portion 12a). In this way, step (a) is completed.

Next, the plate 13 is further lowered while contracting the expansion / contraction mechanism 14. As a result, as shown in FIG. 15C, the cam mold 21 is slid toward the convex portion 12a. Since the premolded product 301 has a surplus portion, the surplus portion projects upward.

Next, as shown in FIG. 15D, the plate 13 is lowered to the bottom dead center, and the portion to be the vertical wall portion is pressed and restrained by the cam mold 21 and the lower mold 12 (convex portion 12a). At this time, the surplus portion is folded between the upper mold 11 and the cam mold 21 to form a protruding portion 115. In this way, step (b) is completed. The press molding is completed as described above, and the press molded product 100 is obtained.

As described above as a third example of the second step, the steps (a) and (b) may be completed at the same time in the second step. By adjusting the shape and arrangement of the molds, steps (a) and (b) can be completed at the same time.

When the second step is performed by hot stamping, when the movement of the dies (press dies 10 and cam dies 21) is completed in order to perform proper quenching in the second step, those dies and the press molded product 100 It is preferable that and are in close contact with each other. The press-molded product 100 obtained in the second step is post-treated as necessary. The obtained molded product is used in combination with other parts as needed.

The second step may be performed using a press die including a pin protruding from at least one of a pair of press dies (upper die and lower die). An example of such a second step is schematically shown in FIG. The press die of FIG. 16 includes a pin 16 protruding from the convex portion 12a of the lower die 12. The upper mold 11 is formed with a hole 11h into which the pin 16 is inserted when the upper mold 11 is lowered. The pin 16 is inserted into the through hole formed in the premolded article 301. By performing the press molding in the second step in that state, the protruding portion can be formed with high accuracy. The press die may have a mechanism in which at least a part of the pin 16 is housed in the lower die 12 when the pin 16 is pressed from above.

Next, in the third step, the metal member (S1) is fixed to the overlapping portion 115d of the press-molded product 100. The above-mentioned method can be applied to the fixing method, and it may be selected according to the shape and application of the press-molded product 100.

When the structural member of the present embodiment includes the member (S2), the member (S2) may be fixed before or after the metal member (S1) is fixed. The above-mentioned method can also be applied to the fixing of the member (S2), which may be selected according to the shape and application of the press-molded product 100.

As described above, the structural member of the present embodiment is obtained. Of course, the structural member obtained in the third step may be further processed and then used as a structural member of an automobile.

The present invention will be described in more detail by way of examples.

(Example 1)
In Example 1, a simulation of a three-point bending test was performed on a structure composed of a press-molded product (P) and a member (S2). For the simulation, general-purpose FEM (finite element method) software (manufactured by LIVERMORE SOFTWARE TECHNOLOGY, trade name LS-DYNA) was used. FIG. 17A schematically shows a cross-sectional view of Sample 1 used in the simulation as a structure containing the press-molded product (P). The structure of FIG. 17A includes a press-molded product 100 and a member (back plate) 201 welded to the flange portion 113 thereof. The size of sample 1 shown in FIG. 17A is as follows. However, the thickness of the steel plate is not considered for the following sizes.
・ Angle X: 180 °
・ Angle Y: 90 °
・ Length of protrusion D: 15 mm
・ Height of vertical wall Hb1: 60mm
-Width between the tips of the two protrusions Wt1: 80 mm
-Distance between two vertical walls (width of top plate) Wb1: 50 mm (80-2D)
-Back plate width Wp1: 90 mm (120-2D)
-Radius of curvature at corners Ra and Rb: 5 mm
・ Longitudinal length: 1000 mm

Further, sectional views of Sample 2 and Sample 3 used in the simulation as the structure of the conventional example are schematically shown in FIGS. 17B and 17C. The sample 2 shown in FIG. 17B includes a press-molded product 1 having a hat-shaped cross section and a back plate 2 welded to a flange portion 1c thereof. The press-molded product 1 includes a top plate portion 1a, a vertical wall portion 1b, and a flange portion 1c. The size of sample 2 shown in FIG. 17B is as follows.
-Width of top plate 1a: 80 mm
-Height of vertical wall 1b: 60 mm
-Width of back plate 2: 120 mm
・ Radius of curvature at corners: 5 mm
・ Longitudinal length: 1000 mm

Sample 2 and Sample 3 have exactly the same structure and differ only in arrangement. Specifically, in the sample 2, the back plate 2 side is arranged on the upper side (impactor side), and in the sample 3, the top plate portion 1a side is arranged on the upper side (impactor side). Hereinafter, the arrangement in which the back plate side is upward (the arrangement of the sample 2) is referred to as the arrangement of the reverse hat. Further, the arrangement in which the top plate portion side is upward (the arrangement of the sample 3) is referred to as the arrangement of the positive hat. As will be described later, collisions that occur in actual structural members mainly occur in the arrangement of positive hats. Therefore, the comparative example of the sample 1 is the sample 3 with the normal hat arrangement, and the sample 2 with the reverse hat arrangement is described as a reference example.

Samples 1 to 3 were assumed to consist of a steel plate having a thickness of 1.4 mm and a tensile strength of 1500 MPa. It was assumed that the flange portion and the back plate of the press-molded product were spot-welded and fixed at a pitch of 40 mm. Samples 1 to 3 were designed so that the mass per unit length in the longitudinal direction was the same.

The method of the three-point bending test used in the simulation is schematically shown in FIG. The three-point bending test was performed by placing the sample on the two fulcrums 5 and pushing the sample from above by the impactor 6. In the test of Example 1, the distance S between the two fulcrums 5 was 400 mm or 700 mm. The radius of curvature of the fulcrum 5 was 30 mm. The radius of curvature of the impactor 6 was set to 150 mm. The collision speed of the impactor 6 was 7.5 km / h.

In the three-point bending test, the impactor 6 was made to collide from above each sample. Specifically, six types of tests shown in Table 1 below were performed. The collision direction of the impactor 6 is indicated by an arrow in FIGS. 17A to 17C.

In tests 1-1 to 1-3 and 2-1 to 2-3, the amount of energy absorbed by each sample when the displacement amount was 100 mm was determined. The results are shown in FIGS. 19A and 19B. FIG. 19A shows the results of tests 1-1 to 1-3 (distance S = 400 mm), and FIG. 19B shows the results of tests 2-1 to 2-3 (distance S = 700 mm). Automobile structural parts that absorb a large amount of energy mean that the safety of occupants in a collision is high.

19A and 19B also show the results when the length D of the protrusion of the sample 1 is 5 mm, 10 mm, 15 mm, and 20 mm. When the length D is 5 mm, only the tip portion of the protruding portion serves as the overlapping portion. All the samples were designed so that the mass per unit length in the longitudinal direction was the same. Furthermore, these figures also show simulation results that do not consider cracks in the steel sheet and cracks in the spot welded portion, and simulation results that take them into consideration.

As shown in FIGS. 19A and 19B, the energy absorption amount of each of the samples 1 having the protrusions was larger than that of the sample 3 (comparative example) in the normal hat arrangement. Furthermore, when cracking was taken into consideration, sample 1 showed higher characteristics than sample 2 (reference example) in many cases. FIG. 19A shows that when the distance S between the fulcrums is 400 mm, the length D of the protruding portion is preferably 10 mm or more. FIG. 19B shows that when the distance S between fulcrums is 700 mm, it is preferable that the length D of the protruding portion is long.

As shown in FIGS. 19A and 19B, in the result of sample 2 (reverse hat arrangement), the energy absorption amount when the cracks of the steel plate and the spot weld are taken into consideration is larger than the energy absorption amount when they are not taken into consideration. It has decreased. This result suggests that when the impactor 6 collides from the back plate side, cracks (for example, cracks in the spot welded portion) are likely to occur.

When a press-molded product having a substantially hat-shaped cross section is used as an automobile or other structural member, the top plate side is often arranged toward the outside of the body. Therefore, it is necessary to assume that the collision at the time of an accident occurs not from the back plate side but from the top plate side. In that respect, even if the characteristics of the sample 2 in the reverse hat arrangement are good, it is often meaningless when actually applied as a structural member. Therefore, the characteristics against collision from the top plate side are important. When compared by collision from the top plate side, Sample 1 showed very excellent characteristics with respect to Sample 3 in the positive hat arrangement. Therefore, the structural member using the press-molded product (P) is very useful for improving the collision safety.

(Example 2)
In Example 2, a three-point bending test was simulated in the same manner as in Example 1 for a sample (Sample 1') in which only the angle X of Sample 1 (D = 15 mm) was changed. The angles X of sample 1'were 90 °, 105 °, 120 °, 135 °, and 180 °. The shape of the press-molded product (P) included in the sample 1'when the angle X is 90 ° is the same as that of the press-molded product 100 shown in FIG. 7.

The energy absorption amount of each sample when the displacement amount was 100 mm was obtained by simulation. The result when the distance S between the fulcrums is 400 mm is shown in FIG. 20A. The result when the distance S between the fulcrums is 700 mm is shown in FIG. 20B. In the simulation of Example 2, cracks in the steel plate and cracks in the spot welded portion were not considered.

As shown in FIGS. 20A and 20B, sample 1'showed better properties than sample 3 in the positive hat arrangement even when the angle X changed. As shown in FIG. 20A, when the distance S between the fulcrums was 400 mm, the larger the angle X, the larger the amount of energy absorbed. On the other hand, as shown in FIG. 20B, when the distance S between the fulcrums was 700 mm, the smaller the angle X, the larger the amount of energy absorbed.

FIG. 21A shows the cross-sectional shape of the sample 1 displaced by the impactor collision in the test of the first embodiment. In sample 1, the vertical wall portion is tilted inward, thereby receiving the load. This is because the angle X is larger than 90 °. FIG. 21B shows the cross-sectional shape of the sample 1'displaced by the impactor collision in the test of Example 2. FIG. 21B shows a sample 1'at an angle X = 90 °. As shown in FIG. 21B, when the angle X = 90 °, the outer steel plate of the sample 1'(the outer steel plate of the protrusion and the steel plate of the vertical wall portion) receives the load as a whole.

As described above, by using the press-molded product (P), a structural member capable of enhancing the collision safety of an automobile can be obtained. Further, by fixing the metal member (S1) to the superposed portion of the press-molded product, a structural member having a high degree of freedom in manufacturing and the reliability of the fixed portion can be obtained.

The present invention can be used for structural members for automobiles.

10: Pair of press molds 11: Upper mold (press mold)
12: Lower mold (press mold)
100: Press-molded products 101, 101a, 101b: Steel plate 111: Vertical wall part 112: Top plate part 113: Flange part 114: Boundary part 115: Protruding part 115d: Overlapping part 200a, 200b, 200c: Structural member (automobile parts) )
201: Other members 301: Pre-molded product 301ae: Surplus part 400: Structural member 410: Metal member D: Length of the protruding part and protruding from the boundary part X: Top plate part and overlapping part Angle to make

Claims (11)

A structural member for automobiles
A press-molded product formed of a single steel plate and a metal member made of a metal plate fixed to the press-molded product are included.
The press-molded product is
Two vertical walls and
The top plate that connects the two vertical walls and
Including a protruding portion protruding from at least one boundary portion of the two boundary portions connecting the vertical wall portion and the top plate portion.
Before SL protrusions have overlapping portions in which the steel sheet to at least the tip is folded in its protrudes from the boundary,
A structural member for an automobile in which the metal member is fixed to the overlapping portion. The structural member for an automobile according to claim 1, wherein the press-molded product includes two protrusions protruding from each of the two boundary portions. The structural member for an automobile according to claim 1 or 2, wherein the angle formed by the top plate portion and the overlapping portion is in the range of 90 ° to 180 °. The metal member is fixed to the press-molded product at one of the vertical wall portion and the top plate portion, and at two locations of the overlapping portion.
The structure for an automobile according to claim 1 or 2, wherein the angle formed by the vertical wall portion or the top plate portion to which the metal member is fixed and the overlapping portion is in the range of 90 ° to 175 °. Element. Any one of claims 1 to 4, wherein the press-molded article and the metal member are fixed by at least one selected from the group consisting of welding, adhesive, brazing, rivets, and friction stir welding. Structural members for automobiles described in the section. The structure for an automobile according to any one of claims 1 to 4, wherein the press-molded product and the metal member are fixed by resistance spot welding in which electrodes are applied to both sides of the fixing portion and welded. Element. The structural member for an automobile according to any one of claims 1 to 6, wherein the press-molded product includes two flange portions extending from the ends of the two vertical wall portions. Including other members consisting of metal plates
The structural member for an automobile according to claim 7, wherein the other member is fixed to the two flange portions so that the press-molded product and the other member form a closed cross section. The press-molded product is a press-molded product that constitutes a portion connected below the A-pillar.
The structural member for an automobile according to any one of claims 1 to 7, wherein the metal member is a member constituting an upper member. The press-molded product is a side sill inner and
The structural member for an automobile according to any one of claims 1 to 7, wherein the metal member is a floor panel. The method for manufacturing a structural member for an automobile according to any one of claims 1 to 10.
The first step of forming a preformed product including the two vertical wall portions and the top plate portion by deforming the material steel plate.
The second step of forming the press-molded product by press-molding the pre-molded product, and
A third step of fixing the metal member to the overlapping portion of the press-molded product is included.
The premolded article includes a surplus portion for forming the protrusion.
A method for manufacturing a structural member for an automobile, wherein in the second step, at least a part of the material steel sheet constituting the surplus portion is folded and overlapped to form the overlapped portion.

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