Joining member, press molding die, joining method, and joining member manufacturing method

Abstract

Provided is a joining technique that yields excellent surface quality without generating quality defects such as cracks. In this joining member, a first member having a protrusion and a second member having a hole portion are joined while superimposed on each other in a plate thickness direction. The protrusion has a length before joining that is longer than the hole portion. The protrusion includes: a convex bent portion that has a smaller width than the hole portion, connects and extends to another portion of the first member, and is formed so as to be bent in the direction of the second member; a concave bent portion that has a smaller width than the hole portion, connects and extends to the convex bent portion, is bent in a direction opposite to the convex bent portion, and is inserted into the hole portion; and a caulking portion that connects and extends to the concave bent portion, has the widest tip, has a tapered shape having a greater width than the hole portion, and is caulked so as to expand the hole portion.

Description

Joining member, press molding die, joining method, and manufacturing method of joining member

[0001] The present invention relates to a joint member, a press molding die, a joining method, and a method for manufacturing a joint member.

[0002] From the perspective of protecting vehicle occupants, improved collision safety is required for automobile bodies. At the same time, it is also important to reduce the weight of automobile bodies and improve fuel efficiency in order to reduce carbon dioxide emissions. To achieve both collision safety performance and lightweight body, the use of high-strength materials in automobile body structural components is increasing year by year. For example, pillar components such as the front pillars and center pillars that form the cabin of an automobile body are important structural components for protecting passengers inside the cabin in the event of a vehicle collision. For this reason, pillar components must be strong enough to withstand collision loads, and high-tensile steel plates with a tensile strength grade of 1470 MPa or higher are also used.

[0003] Figure 17 shows an example of an automobile frame part. The press-molded part 100 consists of a main body part 1B and a reinforcing part 2B. In the example of Figure 17, the main body part 1B has a hat-shaped cross section and is composed of a top plate portion 13, a vertical wall portion 14, a flange portion 15, and a ridge portion connecting these. The reinforcing part 2B is arranged inside the main body part 1B and, in the example of Figure 17, has a U-shaped (groove-shaped) cross section and is composed of a top plate portion 22, a vertical wall portion 23, and a ridge portion connecting these. The main body part 1B and the reinforcing part 2B are joined to each other by resistance spot welding, and a joint 111 is arranged between the top plate portions 13, 22 and the vertical wall portions 14, 23.

[0004] Welding is a typical method for joining parts together. However, when joining dissimilar materials, such as steel and aluminum alloy plates, direct welding is difficult due to differences in melting points and thermal conductivity. In addition, spatter scattered during welding can degrade the surface quality of the product.

[0005] Besides welding, mechanical joining is a commonly known method for joining thin plates. For example, Patent Document 1 discloses a self-piercing rivet that joins overlapping workpieces together using a rivet 1 equipped with a hollow shank 4 having a center hole 3 that opens at the tip. The technology in Patent Document 1 involves driving the rivet by heating a heating area on at least one side of the workpieces, centered on the rivet driving point, until the workpieces reach a predetermined temperature.

[0006] Patent Document 2 discloses a technique in which a plate-shaped upper back panel and a side panel, at least a portion of which overlaps the upper back panel in the thickness direction, are joined by mechanical clinching from the upper back panel side at a plurality of crimping portions. Patent Document 3 discloses a technique in which a plate-shaped fastening material having small holes is placed on a fastening material having large holes, and a burring punch is pressed into the small holes and further pressed to fasten the members by burring.

[0007] Patent Document 4 discloses a method in which resistance spot welding guns are built into a mold in an opposing arrangement, and welding is performed by passing current through the mold at the bottom dead center while forming the overlapping blanks. Furthermore, Non-Patent Document 1 describes a method in which buckling is intentionally caused in the vertical wall of the main body part, and the buckled part functions to lock the inner reinforcing part and hold the reinforcing part.

[0008] JP 2006-007266 A JP 2019-084570 A JP 2020-029876 A JP 01-186227 A

[0009] Combined process of hot stamping and mechanical joining for producing ultra-high strength steel patchwork components, Journal of Manufacturing Processes, 59 (2020), pp. 444-455

[0010] However, the above-mentioned conventional technologies have the following problems to be solved. That is, the method disclosed in Patent Document 1 has a problem of breakage of the joint during forming. When two overlapping and joined blanks are bent, a difference in line length between the inside and outside of the bend causes a misalignment between the blanks.

[0011] Although the method disclosed in Patent Document 2 solves the problem of misalignment between blanks, it has the problem that the two parts separate when removed from the mold in which they were integrally molded, making it impossible to weld them in the next process. To prevent this, it is necessary to join the main part and the reinforcing part simultaneously with molding in the mold, or at least to temporarily fasten them so that they do not separate and remain integrated until they are transported to the subsequent welding process.

[0012] The mechanical joining disclosed in Patent Document 3 involves a large deformation of the material, and therefore, when applied to a low-ductility material, such as a high-tensile steel plate, there is a concern that the material may crack. Furthermore, the method described in Patent Document 4 requires complex equipment, which may result in excessive capital investment.

[0013] The technique described in Non-Patent Document 1 is carried out by hot pressing, which heats and forms the material. This method softens the material, causing local deformation. However, this technique is difficult to apply to high-tensile steel sheets, which are formed by cold pressing to maintain strength.

[0014] The present invention has been made to solve the above-mentioned problems, and its object is to provide a joining technology that is economical and has excellent surface quality, even when using materials with poor ductility such as high-tensile steel plates, without causing quality defects such as cracks.

[0015] The gist of the present invention, which solves the above-mentioned problems, is as follows: [1] A joining member formed by joining a first member having a protrusion and a second member having a hole overlapping each other in the thickness direction, wherein the protrusion has a length longer than the hole before joining, and the protrusion has a convex bent portion that has a width narrower than the hole, is connected to another part of the first member, extends, and is bent toward the second member, a concave bent portion that has a width narrower than the hole, is connected to the convex bent portion, extends, and is bent in the opposite direction from the convex bent portion and is inserted into the hole, and a crimping portion that is connected to the concave bent portion, extends, and has a tapered shape that widens toward its tip, with the tip being wider than the hole, and crimps the hole so as to expand it. [2] In the above [1], the first member has the protrusion on a flat portion, and the second member has the hole on the flat portion, the first member and the second member are integrally formed by overlapping in the plate thickness direction, and have a U-shaped or hat-shaped cross section having at least a top plate portion and a vertical wall portion, and the first member and the second member are joined by press molding at a location corresponding to the flat portion. [3] In the above [2], the flat portion is at least one of the top plate portion and the vertical wall portion. [4] A press molding die for press-forming the joined member described in [2] or [3] above, which overlaps the first member and the second member to integrally form a member with a U-shaped or hat-shaped cross section having at least a top plate portion and a vertical wall portion, and includes a joining portion that joins the two blanks at a location corresponding to the flat portion of the members, the joining portion having a convex push-in portion and a concave first relief portion adjacent to the push-in portion provided on one of a pair of opposing dies, and a concave second relief portion provided on the other die into which the convex push-in portion is inserted. [5] The press molding die described in [4] above, wherein the pair of opposing dies is a pad and a punch. [6] The press molding die described in [4] above, wherein the pair of opposing dies is a die and a punch.[7] A joining method for joining a first member having a protrusion and a second member having a hole by overlapping them in the plate thickness direction, wherein the length of the protrusion before joining is longer than the hole, a first part of the protrusion is connected to another part of the first member and extends, and has a width narrower than the hole, is bent toward the second member to form a convex bent part, a second part of the protrusion is connected to the convex bent part and extends, and has a width narrower than the hole, is bent in the opposite direction to the convex bent part and inserted into the hole to form a concave bent part, a tapered part is connected to the concave bent part and extends, and its width widens towards its tip, and the tip is wider than the hole, and the hole is crimped to expand the crimped part. [8] In the above [7], the first member and the second member are made of metal plates and formed by press forming, and the first member and the second member have a U-shaped cross section consisting of a top plate portion and a vertical wall portion, or a hat-shaped cross section consisting of a top plate portion, a vertical wall portion, and a flange portion, and the joining method includes: a blanking step of processing at least the outer periphery of the metal plate to obtain a first blank and a second blank; a forming step of forming the first blank and the second blank into target shapes by press forming, respectively, to obtain the first member and the second member; and a joining step of joining the first member and the second member by the method described in the above [7]. [9] In the above [8], the joining method includes joining the first member and the second member at at least one of the top plate portion and the flange portion.

[10] In the above [7], the first member has the protrusion on a flat portion, and the second member has the hole on the flat portion, and the first member and the second member are integrally molded by overlapping them in the plate thickness direction to form a member having a U-shaped cross section consisting of a top plate portion and a vertical wall portion, or a hat-shaped cross section consisting of a top plate portion, a vertical wall portion, and a flange portion, and the first member and the second member are joined by press molding at a location corresponding to the flat portion, the method comprising: a convex push-in portion and a concave first escape portion adjacent to the push-in portion provided on one of a pair of opposing dies; and a concave first escape portion provided on the other die, into which the convex push-in portion is inserted.

[11] A joining method comprising: a joining step using a press-forming die having a joining portion having a second relief portion, in which the protruding portion of the first member is connected to and extends to another portion of the first member, a portion having a width narrower than the hole portion is pressed into the hole portion and the second relief portion by the pressing portion, and a crimping portion of the protruding portion having a tapered shape and a tip side wider than the hole portion is brought into contact with a longitudinal edge of the hole portion to raise the crimping portion and position the tip side of the crimping portion within the first relief portion, thereby crimping the hole portion so as to expand the width direction; and a molding step of forming another portion into a target shape.

[12] A joining method according to

[10] or

[11] , wherein the flat portion is at least one of the top plate portion and the vertical wall portion.

[13] A joining method according to

[10] or

[11] , wherein the pair of opposing dies is a pad and a punch, and the pad is lowered to clamp and join the overlapping members with the punch.

[13] In the joining method according to the above

[10] or

[11] , the pair of opposing dies is a die and a punch, and the die is lowered to clamp and join the overlapped members with the punch.

[14] A method for manufacturing a joined member, comprising the step of overlapping and joining the first member and the second member using the joining method according to any one of the above [7] to

[13] .

[0016] According to the present invention, even materials with poor ductility such as high-tensile steel plates can be stably joined without causing quality defects due to cracks, etc. Because it is a mechanical joining technology, there is no deterioration in surface quality as occurs with welding.

[0017] FIG. 1 is a schematic perspective view showing a joint of a joined member according to one embodiment of the present invention. FIG. 2 is a side view of a joint according to the embodiment. FIG. 3 is a top view of a joint according to the embodiment. FIG. 4 is a schematic perspective view of a joint for explaining a joining method according to the embodiment. FIG. 5 is a cross-sectional view taken along the X-X line in FIG. 4 , showing a widthwise central cross section of a joint for explaining a joining method according to the embodiment. FIG. 6 is a top view of a joint of a first member according to the embodiment before joining. FIG. 7 is a top view of a joint of a second member according to the embodiment. FIG. 8 is a schematic top view showing a positional relationship between a protrusion and a hole according to the embodiment. FIG. 9 is a schematic perspective view showing a joint of a joined member according to another embodiment of the present invention. FIG. 10 is a schematic perspective view showing a press-formed member as an example of the joined member according to the embodiment. FIG. 11 is a schematic cross-sectional view showing the configuration and movement of a die for forming the press-formed member according to the embodiment. FIG. 12 is a schematic perspective view showing the behavior of a blank at a joint during press forming of the press-formed member according to the embodiment. FIG. 13 is a schematic perspective view showing another example of a press-formed member. FIG. 14 is a schematic perspective view showing one flow of a manufacturing process for the press-formed member. FIG. 15 is a schematic perspective view showing another flow of a manufacturing process for the press-formed member. FIG. 16 is a schematic perspective view showing another example of a press-formed member. FIG. 17 is a schematic perspective view showing a conventional press-formed member.

[0018] Hereinafter, embodiments of the present invention will be described in detail. Note that the drawings are schematic and may differ from the actual embodiments. Furthermore, the following embodiments exemplify components and methods for embodying the technical idea of ​​the present invention, and are not intended to limit the configuration to the following. In other words, the technical idea of ​​the present invention can be modified in various ways within the technical scope described in the claims.

[0019] First Embodiment In this embodiment, a member is formed by joining two plate-like members to be joined, and the following description focuses on the joint. Therefore, the members to be joined may be flat plate-like members or structural members formed into a three-dimensional shape. There are no particular limitations on the shape.

[0020] (Joining Member) FIGS. 1 to 3 show an example of a joining portion of a joining member. FIG. 1 is a schematic perspective view, FIG. 2 is a schematic side view, and FIG. 3 is a top view. In the figures, symbol 1 represents a first member, and symbol 2 represents a second member. Symbol 12 represents a protrusion provided on the first member 1, and symbol 21 represents a hole provided on the second member 2. FIG. 6 is a top view of the first member 1 before joining, FIG. 7 is a top view of the second member 2, and FIG. 8 is a top view showing the positional relationship between the protrusion 12 and the hole 21 before joining when the first member 1 and the second member 2 are overlapped. The joining portion 110 of the joining member according to this embodiment is a portion where the first member 1 and the second member 2 are overlapped and joined in the plate thickness direction. Note that the protrusion 12 here has a substantially rectangular shape before joining, as exemplified in FIG. 6. The side of the protrusion 12 that connects to another portion of the first member is referred to as the connecting portion 13. The direction in which the protrusion 12 extends from the connection portion 13 is defined as the longitudinal direction L, and the direction in the plane of the protrusion 12 and perpendicular to the longitudinal direction L is defined as the width direction W. The hole 21 of the second member 2 is rectangular, and the longitudinal direction L and width direction W are defined in the same way as the protrusion 12 when it is superimposed on the first member 1. In this embodiment, the protrusion 12 is provided within the plane of the first member 1 and is surrounded by the frame portion 11 of the other part. Furthermore, the hole 21 is surrounded by the frame portion 22 of the second member 2 that constitutes each side of the hole 21.

[0021] As shown in FIG. 8, the length L of the protrusion 12 before joining １ is the length L of the hole 21 ２ The protrusion 12 has a convex bent portion 12A, a concave bent portion 12B, and a crimped portion 12C in a joined state. The convex bent portion 12A is, for example, connected to the frame portion 11 by a connecting portion 13 and extends, and is formed by being bent in the direction of the second member while contacting one edge of the hole portion 21 in the longitudinal direction L. The concave bent portion 12B is connected to the convex bent portion 12A and extends, and is formed by being bent in the opposite direction to the convex bent portion 12A, and is inserted into the hole portion 21. The convex bent portion 12A and the concave bent portion 12B may be formed as a continuous curved surface, or a flat portion may be sandwiched between them. The width W of the convex bent portion 12A is １Ａ and the width W of the concave bent portion 12B １Ｂ are the width W of the hole 21 ２The crimped portion 12C is connected to the concave bent portion 12B and extends, and the width of the crimped portion 12C increases toward the tip in the longitudinal direction L. １Ｃ is the width of the hole W ２ The crimping portion 12C has a tapered shape with a wider width. The crimping portion 12C crimps the both edges of the hole 21 in the width direction W while contacting the other edge of the hole 21 in the longitudinal direction L, thereby joining the first member 1 and the second member 2. １ is approximately equal to the line length along the curved surface from the connection portion 13 of the protrusion 12 to the tip of the crimped portion 12C after joining.

[0022] (Joining Method) The joining method according to the first embodiment will be described with reference to FIGS. 4 and 5. FIGS. 4 and 5 are a perspective view and a cross-sectional view taken along the X-X line at the center of the width direction, respectively, showing the first member 1 and the second member 2 superimposed on each other, from (a) a state before joining to (c) a state after joining is completed. In the blank state, the first member 1 is machined to have a protrusion 12 cut out and surrounded by a frame 11, as shown in FIG. 6. In the blank state, the second member 2 is machined to have a hole 21 surrounded by a frame 22, as shown in FIG. 7. The machining method used here may be any of shearing, laser machining, electric discharge machining, and the like, and is not limited thereto.

[0023] In the example of FIG. 6, the protrusion 12 extends from the connection portion 13 before joining, and has a width W of the hole 21. ２ Narrower width W １Ａ =W １Ｂ Furthermore, the protrusion 12 extends from the parallel portion 12D and widens toward the tip, with a width W １Ｃ is the width of the hole W ２ It has a caulking portion 12C having a tapered shape with a wider width.

[0024] In the joining method according to this embodiment, first, the first member 1 and the second member 2 are overlapped at a predetermined position as shown in FIGS. 4( a) and 5(a). It is preferable to arrange the protrusion 12 and the hole 21 as shown in FIG. 8. The widthwise edge of the parallel portion 12D of the protrusion 12 is inside the widthwise edge of the hole 21, and the tip of the crimped portion 12C is outside the hole 21. It is preferable to align the widthwise center line of the protrusion 12 with the widthwise center line of the hole 21. Positioning pins or the like may be used to improve the positioning accuracy of the overlap.

[0025] Next, as shown in Figures 4(b) and 5(b), the parallel portion 12D is pressed toward the second member. A first portion of the parallel portion 12D extending from the connection portion 13 with the other portion of the first member 1 is bent toward the second member to form the convexly bent portion 12A. At this time, it is preferable that the connection portion 13 side of the parallel portion 12D is left a predetermined amount beyond one edge of the hole 21 in the longitudinal direction, and that the convexly bent portion 12A bends while contacting that edge.

[0026] At the same time, the back surface of the protrusion 12 comes into contact with the other longitudinal edge of the hole 21, and the crimped portion 12C slides and is inserted into the hole 21 (FIGS. 4(b) and 5(b)). At this time, the remaining second portion of the parallel portion 12D located between the convex bent portion 12A and the crimped portion 12C bends in the opposite direction to the convex bent portion to form the concave bent portion 12B that is inserted into the hole 21. The crimped portion 12C then rises and is inclined at an angle relative to the surface of the second member 2 in the longitudinal direction.

[0027] Further, as the parallel portion 12D, i.e., the concave bent portion 12B, continues to be pressed in, both widthwise ends of the crimping portion 12C come into contact with both widthwise edges of the hole 21. As shown in Figures 4(c) and 5(c), the pressing of the parallel portion 12D is completed when the crimping portion 12C pushes open and crimps the hole 21 with a predetermined load and stroke. This joins the first member 1 and the second member 2.

[0028] Second Embodiment This embodiment relates to a so-called patchwork press forming method and a press forming die for achieving this method, in which two flat blanks (members) are integrally formed using a single die. The difference from conventional press forming is that the blanks are set in the die in an unbonded state, and are joined simultaneously during forming.

[0029] The press-formed member targeted in this embodiment is formed by molding overlapping members having at least a top plate portion and vertical wall portions. An example of a press-formed member 100 according to this embodiment is shown in a schematic perspective view in FIG. 10 . As shown in FIG. 10 , a main body component 1A having a hat-shaped cross section and a reinforcing component 2A having a U-shaped (groove-shaped) cross section are overlapped inside the main body component 1A and joined at the center of the width of the top plate portion 113. The main body component 1A comprises a top plate portion 113, vertical wall portions 114, flange portions 115, and ridge portions connecting these. The reinforcing component 2A comprises a top plate portion 122, vertical wall portions 123, and ridge portions connecting these. A mechanical joint 110 is arranged on the top plate portions 113 and 122.

[0030] 11 is a schematic cross-sectional view showing the configuration and movement of a press molding die suitable for use in the press molding method according to this embodiment. The upper die 3 is composed of a die 31 and a pad 32. The pad 32 is connected to a pressure device serving as a biasing means, such as a gas cushion, hydraulic device, or spring, and is configured to apply a downward load to the top plate portion. The lower die 4 is a punch 41. The top plates of the pad 32 and punch 41 have joints for joining the two pieces, but since we will first explain the molding of the entire part, we will omit an explanation of the joint and will explain it in detail later.

[0031] 11(a), a first blank 1A, which will become the main body part, and a second blank 2A, which will become the reinforcing part, are stacked and set on a punch 41. The first blank 1A and the second blank 2A ​​are aligned using a standard method such as a pin and hole, and are set so that the joints of each blank are aligned in the correct positions on each mold.

[0032] 11(b), the die 31 and pad 32 of the upper mold 3 are lowered, and the portions of the blanks 1 and 2 corresponding to the top plate portions 113 and 122 are pressed downward by the pad 32. As a result, the top plate portions 113 and 122 are pressed and held between the pad 32 and the punch 41.

[0033] In this state, as shown in Figure 11 (c), the die 31 of the upper mold 3 is further lowered to simultaneously bend and form the two blanks 1 and 2, thereby forming the vertical wall portions 114, 123 and the flange portion 115, thereby forming the target shape.

[0034] (Mechanical Joining) Next, the joining of two blanks will be described. In this embodiment, the blanks are mechanically joined by the movement of the mold during press forming. In this embodiment, the explanation will focus on the joint 110 of the top plate portions 113 and 122.

[0035] FIG. 4 is a schematic perspective view showing the behavior of two blanks 1A and 2A during press forming at the joint 110. FIG. 6 is a top view of the protrusion 12 formed in the first blank 1A before joining. FIG. 7 is a top view of the hole 21 formed in the second blank 2A. FIG. 8 is a top view showing the positional relationship between the protrusion 12 and the hole 21 when the first blank 1A and the second blank 2A ​​are overlapped. As shown in FIG. 6, the protrusion 12 has a substantially rectangular shape before joining, and the edge connecting to another portion of the first blank 1A is defined as the connection portion 13. The direction in which the protrusion 12 extends from the connection portion 13 is defined as the longitudinal direction L, and the direction in the plane of the protrusion 12 and perpendicular to the longitudinal direction L is defined as the width direction W. The hole 21 of the second blank 2A ​​is rectangular, and when overlapped, the longitudinal direction L and width direction W are defined in the same way as the protrusion 12. The machining of the protrusions 12 on the first blank 1A and the machining of the rectangular holes 21 on the second blank 2A ​​may be performed by any of shearing, laser machining, electric discharge machining, etc. The alignment of the protrusions 12 and the holes 21 may be performed in the same manner as in the first embodiment.

[0036] Figure 12 is a schematic enlarged cross-sectional view showing the behavior of the dies 3, 4 and blanks 1A, 2A in the vicinity of the joint 110 shown in the X-X cross section of Figure 4. The joint portion of the pad 32 that becomes the upper die 3 has a convex push-in portion 32A and a concave first escape portion 32B adjacent to the push-in portion 32A. The joint portion of the punch 41 that becomes the lower die 4 has a concave second escape portion 41A.

[0037] After the blanks 1 and 2 are set in the predetermined positions, the pad 32 is lowered so that the pressing portion 32A of the pad 32 contacts the parallel portion 12D of the protruding portion 12, as shown in FIG. 12( a). Then, as the pad 32 is lowered, the pressing portion 32A is inserted into the hole 21, as shown in FIG. 12( b). The parallel portion 12D of the protruding portion 12 is then bent. A first portion of the parallel portion 12D, extending from the connection portion 13 with the other portion of the first blank 1A, is bent toward the second blank 2A ​​to form the convex bent portion 12A. At this time, it is preferable that the connection portion 13 side of the parallel portion 12D is left a predetermined amount beyond one longitudinal edge of the hole 21, and the convex bent portion 12A is bent while contacting that edge.

[0038] At this time, the back surface of the protruding portion 12 of the first blank comes into contact with the other longitudinal edge of the hole 21 of the second blank, causing the crimped portion 12C to rise. The remaining second portion of the parallel portion 12D, located between the convex bent portion 12A and the crimped portion 12C, bends in the opposite direction to the convex bent portion to form the concave bent portion 12B that is inserted into the hole 21. The convex bent portion 12A and the concave bent portion 12B may be continuously curved or may have a flat portion sandwiched between them. The crimped portion 12C forms an angle with respect to the second blank. When the protruding portion 12 is pressed in, the second relief portion 41A of the punch 41 prevents contact between the concave bent portion 12B of the protruding portion 12 and the lower die 4. Furthermore, when the crimped portion 12C rises, the first relief portion 32B of the pad 32 prevents contact between the tip of the crimped portion 12C and the upper die 3.

[0039] Further, as pad 32 continues to be pressed in, crimping portion 12C is inserted into hole 21, as shown in Figure 12(c) . When the portion of crimping portion 12C whose width is equal to or greater than the width of hole 21 is inserted into hole 21, crimping portion 12C crimps hole 21 so as to expand it in the width direction. This joins two members 1 and 2. At the point in time shown in Figure 12(c) , pad 32 and punch 41 press and hold the two blanks together, and while maintaining this state, die 31 forms vertical wall portions 114, 123 and flange portion 115.

[0040] In the above example, an example of a mold is shown in which the pad 32 of the upper mold 3 has a pushing portion 32A and a first escape portion 32B, and the lower mold 4 has a second escape portion 41A, but the lower mold 4 may have a pushing portion and a first escape portion, and the upper mold 3 may have a second escape portion.

[0041] Furthermore, although the above description has been given of an example in which the joining portion 110 is provided on the top plate portions 113, 122, the joining portion 110 may also be provided on the vertical wall portions 114, 123 as shown in Figure 13. In this case, the joining occurs when the die 31 and punch 41 clamp the two blanks together at the bottom dead center of the press as shown in Figure 11(c). For example, it is preferable to employ a cam mechanism in which the pressing portion of the die 31 moves in a direction perpendicular to the surfaces of the vertical wall portions 114, 123.

[0042] In the case of a subsequent welding process, the joints 110 only need to have a bonding strength sufficient to prevent separation of the overlapping blanks when they are integrally formed. If it is predicted that the bonding strength is insufficient with a predetermined number of joints 110, the number of joints 110 may be increased.

[0043] Third Embodiment A third embodiment of the present invention relates to a method for mechanically joining press-formed members having a U-shaped cross section consisting of a top plate portion and a vertical wall portion, or a hat-shaped cross section consisting of a top plate portion, a vertical wall portion, and a flange portion. For example, as shown in Figure 10, a press-formed member 100 will be described as an example, in which a first member 1 having a hat-shaped cross section and a second member 2 having a U-shaped cross section are overlapped on the inside thereof and joined at the center of the top plate portions 113, 122.

[0044] FIG. 14 is a schematic perspective view showing the flow of the manufacturing process for the press-formed member 100 according to the embodiment. Here, the blank that will become the first member 1 is referred to as the first blank 1A, and the blank that will become the second member 2 is referred to as the second blank 2A. First, in the blank processing step, the outer periphery of each blank 1A, 2A, is processed into a blank shape ( FIGS. 14( a) and 14(b) ). Furthermore, a protrusion 12 is formed at a location corresponding to the joint 110 of the first blank 1A ( FIG. 14(a) ). Then, a rectangular hole 21 is formed at a location corresponding to the joint 110 of the second blank 2A ​​( FIG. 14(b) ). FIGS. 6 and 7 show examples of the protrusion 12 and the hole 21, respectively, in top views. Note that the protrusion 12 has a substantially rectangular shape before joining, as illustrated in FIG. 6 , and the edge that connects to the other portion of the first blank 1A is referred to as the connecting portion 13. The direction in which the protrusion 12 extends from the connecting portion 13 is defined as the longitudinal direction L, and the direction in the plane of the protrusion 12 and perpendicular to the longitudinal direction L is defined as the width direction W. The hole 21 of the second blank 2A ​​is rectangular, and the longitudinal direction L and width direction W are defined in the same way as the protrusion 12 when they are stacked. The length of the protrusion 12 is longer than the length of the hole. Furthermore, the width varies depending on the longitudinal position, and the protrusion 12 has a parallel portion 12D that is narrower than the hole 21 and a tapered crimped portion 12C that is widest at its tip and wider than the hole. Here, the machining of the protrusion 12 on the first blank 1A and the machining of the rectangular hole 21 on the second blank 2A ​​in the blank machining process are not limited to shearing, laser machining, electric discharge machining, etc.

[0045] Next, in the forming step, the first blank 1A is press-formed into a part shape with a hat-shaped cross section consisting of a top plate portion 113, vertical wall portions 114, and flange portions 115 to obtain the first member 1 (FIG. 14(c)).Then, the second blank 2A ​​is press-formed into a part shape with a U-shaped cross section consisting of a top plate portion 122 and vertical wall portions 123 to obtain the second member 2 (FIG. 14(d)).Here, bending, drawing, etc. can be applied as the press forming method, and there are no particular limitations.

[0046] In the subsequent joining process, the first member 1 and the second member 2 are first overlapped in the thickness direction. FIG. 8 is a top view showing the positional relationship between the protrusion 12 and the hole 21 when the first member 1 and the second member 2 are overlapped. The protrusion 12 and the hole 21 are preferably arranged as shown in FIG. 8. The widthwise edge of the parallel portion 12D of the protrusion 12 is positioned inside the widthwise edge of the hole 21, and the tip of the crimped portion 12C is positioned outside the hole 21. It is preferable to align the widthwise center line of the protrusion 12 with the widthwise center line of the hole 21. As described above, since precision in the relative positioning of the two members is required, it is recommended to use positioning pins or the like to set the members.

[0047] After the components are set, the joining portion 110 is pressed with a mold to join them. Figures 4(a) to 4(c) show perspective views of the joining state from the unjoined state to the completed joining state, respectively. Figure 12 shows a schematic cross-sectional view of the joining portion taken along the X-X cross section at the center of the width direction. The upper mold 3 has a convex pressing portion 32A and a concave first relief portion 32B adjacent to the pressing portion 32A. The lower mold 4 has a concave second relief portion 41A. The upper mold 3 is lowered, and the pressing portion 32A of the pad 32 contacts the parallel portion 12D of the protruding portion 12 as shown in Figure 12(a). Then, as the pad 32 descends, the pressing portion 32A is inserted into the hole 21 as shown in Figure 12(b). The parallel portion 12D of the protruding portion 12 is then bent and deformed. Of the parallel portion 12D, a first portion extending from a connection portion 13 with another portion of the first member 1 is bent toward the second member 2 to form a convexly bent portion 12A. At this time, it is preferable that the connection portion 13 side of the parallel portion 12D is left a predetermined amount beyond one edge of the hole 21 in the longitudinal direction, and that the convexly bent portion 12A bends while contacting that edge.

[0048] At this time, the back surface of the protruding portion 12 of the first member 1 comes into contact with the other longitudinal edge of the hole 21 of the second member 2, causing the crimped portion 12C to rise. At this time, the remaining second portion of the parallel portion 12D located between the convex bent portion 12A and the crimped portion 12C bends in the opposite direction to the convex bent portion 12A to form the concave bent portion 12B that is inserted into the hole 21. The convex bent portion 12A and the concave bent portion 12B may be continuously curved, or a flat portion may be sandwiched between them. The crimped portion 12C is angled relative to the second blank. Here, when the protruding portion 12 is pressed in, the second relief portion 41A of the punch 41 prevents the concave bent portion 12B of the protruding portion 12 from coming into contact with the lower die 4. Furthermore, when the crimped portion 12C rises, the presence of the first relief portion 32B in the pad 32 makes it possible to avoid contact between the tip of the crimped portion 12C and the upper die 3.

[0049] 12C, when the pad 32 is further pressed in, the crimping portion 12C is inserted into the hole 21. When the portion of the crimping portion 12C whose width is equal to or greater than the width of the hole 21 is inserted into the hole 21, the crimping portion 12C crimps the hole 21 so as to expand it in the width direction. In this way, the two members 1 and 2 are joined.

[0050] (Fourth embodiment) As described in the third embodiment, in the joining process, it is necessary to align the protrusion 12 of the first member 1 with the hole 21 of the second member 2 with high precision. If they are pre-machined in the blanking process, the positions of the protrusion 12 and the hole 21 may vary during the forming process. In the fourth embodiment of the present invention, the protrusion 12 and the hole 21 are formed in the part after press forming.

[0051] FIG. 15 is a schematic perspective view showing the manufacturing process flow for the press-formed member 100 according to the second embodiment. In the blanking process, the outer peripheries of the first blank 1A and the second blank 2A ​​are machined into a blank shape ( FIGS. 15( a) and 15(b) ). Next, in the forming process, the first blank 1A is press-formed into a hat-shaped cross-section consisting of a top plate portion 113, vertical wall portions 114, and flange portions 115 to obtain the first member 1 ( FIG. 15(c) ). Then, the second blank 2A ​​is press-formed into a U-shaped cross-section consisting of a top plate portion 122 and vertical wall portions 123 to obtain the second member 2 ( FIG. 15(d) ). Next, in the example of FIG. 7 , a protrusion 12 is formed on the top plate 113 of the first member 1 ( FIG. 15(e) ). Then, a hole 21 is formed in the top plate portion 122 of the second member 2 ( FIG. 15(f) ). In the joining process, the protrusion 12 and the hole 21 are aligned and mechanically joined, as in the third embodiment. In the fourth embodiment, the protrusion 12 and the hole 21 are formed after each member is molded, so that the two members can be set with high positional accuracy during joining.

[0052] Fifth Embodiment The examples described above all relate to press-formed members in which a second member 2 having a U-shaped cross section is placed inside a first member 1 having a hat-shaped cross section and joined together. However, as shown in Figure 16, a press-formed member according to a fifth embodiment can also be provided in which two hat-shaped cross-section members 1 and 2 are joined together at flange portions 115 and 124.

[0053] Sixth Embodiment The joining method described above is based on the assumption that the first member 1 and the second member 2 are joined at a certain point inside each other, but the first member 1 and the second member 2 may be joined at an end of the first member 1 as shown in Fig. 9. In this case, the protrusion 12 is processed to protrude from the end of the first member 1.

[0054] (Other Conditions) The present invention is intended to be applied for the purpose of temporary joining to connect components together before the final welding process of the components. Therefore, it is sufficient that the bonding strength is sufficient to prevent the components from separating after temporary joining. If the bonding strength is insufficient, the number of bonding portions can be increased.

[0055] In the above example, the protrusion is substantially rectangular, and the hole is rectangular. The relative dimensional relationship between the protrusion and the hole is determined by the length L of the protrusion. １ is the length of the hole L ２ The width W of the convex and concave bends is larger than １Ａ , W １Ｂ is the width of the hole W ２ Narrower, maximum width W of the crimped part １Ｃ is the width of the hole W ２ It needs to be wider. Length of protrusion L １ is approximately equal to the line length along the curved surface from the connection part of the protrusion to the tip of the crimped part after joining. As long as these relative dimensional relationships are satisfied, there are no restrictions on the length, width, shape, or ratio of the protrusion and hole. If the protrusion deforms due to the weight of the parts or external load after joining, causing gaps between the parts, it is advisable to make the protrusion and hole wider to make them less susceptible to deformation. For example, this method can be applied to steel plates with a tensile strength of 270 to 1800 MPa and a plate thickness of 0.7 to 2.3 mm. The dimension of the protrusion is defined as length L １ ×Maximum width W １Ｃ The hole dimensions are 10 to 50 mm x 5 to 50 mm, and the length L ２ ×Width W ２ The dimensions of the crimped portion can be 7 to 35 mm x 5 to 50 mm. The taper opening angle φ of the crimped portion can be 0.5 to 10°. The angle θ between the crimped portion and the surface of the second member is preferably 30° or more and less than 90°.

[0056] <Method for manufacturing bonded member> The bonding method according to the above embodiment includes a bonding step of bonding a first member 1 and a second member 2, and can be used to manufacture a bonded member 100 in which, for example, a first member 1 and a second member 2 having a U-shaped cross section or a hat-shaped cross section are bonded. This method for manufacturing the bonded member 100 may include a welding step. It may also include a step of applying an adhesive before the bonding step. In this case, the mechanical bonding according to the above embodiment may be used to cure the bonded members with the adhesive.

[0057] According to the present invention, a joined member and joining method are provided that apply bending deformation to members and further utilize caulking at the edge. Damage to the members is less than with conventional joining methods that apply large plastic deformation. This enables stable joining without causing quality defects due to cracks, even with materials with poor ductility such as high-tensile steel plates. Furthermore, for example, because parts formed by press forming are obtained in a temporarily joined state, welding is easier in the subsequent welding process, contributing to cost reduction.

[0058] 100 Joining member (press-formed member) 110 (mechanical) joining portion 111 (welded) joining portion 1 First member 1A First blank (main body part) 1B First member (main body part) 11 Frame portion 12 Protruding portion 12A Convex bent portion 12B Concave bent portion 12C Caulking portion (tapered) 12D Parallel portion 13 Connection portion 113 (main body part) Top plate portion 114 (main body part) Vertical wall portion 115 Flange portion 2 Second member 2A Second blank (reinforcing part) 2B Second member (reinforcing part) 21 Hole portion 22 Frame portion 122 (reinforcing part) Top plate portion 123 (reinforcing part) Vertical wall portion 124 (reinforcing part) Flange portion 3 Upper mold 31 Die 32 Pad 32A Pressing portion 32B (First) Relief portion 4 Lower die 41 Punch 41A (Second) Relief portion

Claims

1. A joined member in which a first member having a protrusion and a second member having a hole are joined by being overlapped in the plate thickness direction, wherein the protrusion has a length longer than that of the hole before joining, the protrusion has a width narrower than that of the hole and is connected to another part of the first member and extends and bends in the direction of the second member to form a convex bent portion, the protrusion has a width narrower than that of the hole and is connected to the convex bent portion and extends and bends in the direction opposite to the convex bent portion to form a concave bent portion inserted into the hole, and the concave bent portion is connected and extends and has a tapered shape in which the width widens toward the tip and the tip has a width wider than that of the hole, and a caulking portion that caulks so as to expand the hole.

2. The first member has the protrusion on a flat portion, the second member has the hole on a flat portion, the first member and the second member are overlapped in the plate thickness direction and integrally formed, have a U-shaped cross section or a hat-shaped cross section having at least a top plate portion and a vertical wall portion, and the first member and the second member are joined by press forming at a location corresponding to the flat portion. The joined member according to claim 1.

3. The joined member according to claim 2, wherein the flat portion is at least one of the top plate portion and the vertical wall portion.

4. A press forming die for press forming the joined member according to claim 2 or 3, wherein the first member and the second member are overlapped to integrally form a member having a U-shaped cross section or a hat-shaped cross section having at least a top plate portion and a vertical wall portion, and a joining portion for joining the two blanks at a location corresponding to the flat portion of the member is provided. The joining portion has a convex pushing portion provided on one of a pair of opposing dies and a concave first escape portion adjacent to the pushing portion, and a concave second escape portion provided on the other die into which the convex pushing portion is inserted. Press forming die.

5. The press forming die according to claim 4, wherein the pair of opposing dies are a pad and a punch.

6. The press forming die according to claim 4, wherein the pair of opposing dies are a die and a punch.

7. A joining method for joining a first member having a protrusion and a second member having a hole portion by overlapping them in the plate thickness direction, wherein the length of the protrusion before joining is made longer than the hole portion, and the first member is connected to another portion of the first member and extended, and a first portion of the protrusion having a width narrower than the hole portion is bent in the direction of the second member to form a convex bent portion, and the convex bent portion is connected and extended, and a second portion of the protrusion having a width narrower than the hole portion is bent in the direction opposite to the convex bent portion and inserted into the hole portion to form a concave bent portion, and a tapered shape portion that is connected and extended to the concave bent portion and whose width expands toward the tip and whose tip has a width wider than the hole portion expands the hole portion and caulks it to form a caulked portion.

8. The joining method according to claim 7, wherein the first member and the second member are made of a metal plate and are formed by press molding, and the method includes a blank processing step of processing at least the outer periphery of the metal plate to obtain a first blank and a second blank, a molding step of molding the first blank and the second blank into a target shape by press molding to obtain the first member and the second member, and a joining step of joining the first member and the second member by the method according to claim 7.

9. The joining method according to claim 8, wherein the first member and the second member are joined at at least one of the top plate portion and the flange portion.

10. The first member has the protruding portion on a flat portion, the second member has the hole portion on a flat portion, the first member and the second member are superposed in the plate thickness direction and integrally formed, and a member having a U-shaped cross section composed of a top plate portion and a vertical wall portion, or a hat-shaped cross section composed of a top plate portion, a vertical wall portion, and a flange portion is formed, and the first member and the second member are joined by press forming at a location corresponding to the flat portion. A press forming die including a joining portion having a convex pushing portion provided on one of a pair of opposing dies and a concave first relief portion adjacent to the pushing portion, and a concave second relief portion provided on the other die into which the convex pushing portion is inserted is used. A portion of the protruding portion of the first member that extends connected to another portion of the first member and has a width narrower than the hole portion is pushed into the hole portion and the second relief portion by the pushing portion, and a caulking portion having a tapered shape and a wider width at the tip side than the hole portion among the protruding portions is brought into contact with an edge in the longitudinal direction of the hole portion to raise the caulking portion and arrange the tip side of the caulking portion in the first relief portion, and a caulking step of caulking so that the caulking portion expands the hole portion in the width direction, and a forming step of forming other portions into a target shape are included. The joining method according to claim 7.

11. The flat portion is at least one of the top plate portion and the vertical wall portion. The joining method according to claim 10.

12. The pair of opposing dies are a pad and a punch, and the pad is lowered and the superposed members are clamped and joined by the punch. The joining method according to claim 10 or 11.

13. The pair of opposing dies are a die and a punch, and the die is lowered and the superposed members are clamped and joined by the punch. The joining method according to claim 10 or 11.

14. A method for manufacturing a joined member including a step of superposing and joining the first member and the second member using the joining method according to any one of claims 7 to 13.

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