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

Abstract

Provided is a joining technology that achieves excellent surface quality without causing quality defects such as cracks. A joining member is formed by joining a first member having a protrusion and a second member having a hole overlapping each other in the thickness direction, the protrusion having a length longer than the hole before joining, the protrusion including: a convex bent portion having a width narrower than the hole, connected to another part of the first member, extending and bent toward the second member; a concave bent portion having a width narrower than the hole, connected to the convex bent portion, extending and bent in the opposite direction from the convex bent portion, and inserted into the hole; and a crimping portion that connects to the concave bent portion, extends, has a tapered shape that is widest at its tip and wider than the hole, and crimps to expand the hole.

Description

[Technical Field]

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

[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] FIG. 17 shows an example of an automobile frame part. The press-molded part 100 is made up of a main body part 1B and a reinforcing part 2B. In the example of FIG. 17, the main body part 1B has a hat-shaped cross section and is made up of a top plate part 13, a vertical wall part 14, a flange part 15, and a ridge part connecting these. The reinforcing part 2B is arranged inside the main body part 1B and, in the example of FIG. 17, has a U-shaped (groove-shaped) cross section and is made up of a top plate part 22, a vertical wall part 23, and a ridge part connecting these. The main body part 1B and the reinforcing part 2B are joined together by resistance spot welding, and a joint part 111 is arranged between the top plate parts 13, 22 and the vertical wall parts 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 multiple 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] Also, 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 them 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 internal reinforcing part and hold the reinforcing part. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-007266 [Patent Document 2] Japanese Patent Application Publication No. 2019-084570 [Patent Document 3] Japanese Patent Publication No. 2020-029876 [Patent Document 4] Japanese Patent Application Publication No. 01-186227 [Non-patent literature]

[0009] [Non-Patent Document 1] 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 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the above-mentioned conventional techniques 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. The reason is that when two overlapping and joined blanks are bent, a difference in line length between the inside and outside of the bend causes 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 together 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 causes a large deformation of the material, and therefore there is a concern that cracks may occur in the material when applied to a low-ductility, high-tensile steel plate, for example. Furthermore, the method described in Patent Document 4 requires complex equipment, which may require excessive capital investment.

[0013] The technology described in Non-Patent Document 1 is implemented using a hot press, which heats and forms the material. This method softens the material, causing localized deformation. However, this technology 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. [Means for solving the problem]

[0015] The gist of the present invention, which solves the above problems in financing, is as follows. [1] A joining member in which a first member having a protrusion and a second member having a hole are overlapped and joined 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 to the convex bent portion, and is inserted into the hole, and a tapered portion that is connected to the concave bent portion, extends, and widens toward the tip, having a tapered shape whose tip is wider than the hole, and is used to crimp the hole so as to expand it. [2] In the above [1], the first member has the protrusion on the 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 thickness direction, and have a U-shaped or hat-shaped cross section with 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 joining member according to the above item [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-molding the joining 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 is provided with a joining portion that joins the two blanks at a location corresponding to the flat portion of the members, and the joining portion has 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 second escape portion provided on the other die and into which the convex push-in portion is inserted. [5] In the above [4], the pair of opposing dies is a pad and a punch, which is a press molding die. [6] In the above [4], the pair of opposing dies is a die and a punch, which is a press molding die. [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 toward the 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 method for joining 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 by press forming includes: a blanking process for processing at least the outer periphery of the metal plate to obtain a first blank and a second blank; a forming process for forming the first blank and the second blank into a target shape by press forming, respectively, to obtain the first member and the second member; and a joining process for joining the first member and the second member by the method described in the above [7]. [9] The joining method according to the above item [8], wherein the first member and the second member are joined to 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 a flat portion, and the first member and the second member are stacked in a thickness direction to be integrally molded, and 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 is molded, and the first member and the second member are joined by press molding at a location corresponding to the flat portion, wherein the first member and the second member are joined by press molding, and the first member and the second member are joined by press molding, and the first member and the second member are joined by press molding, and the first member and the second member are joined by press molding, and the first member and the second member are joined by press molding, and the first member and the second member are joined by press molding, and the second member and the first member are joined by press molding, and the second member and the second member are joined by press molding, and the first member and the second ... and a second relief portion for connecting the protruding portion of the first member to another portion of the first member, and using the pressing portion to press the portion of the protruding portion having a width narrower than the hole portion into the hole portion and the second relief portion, and bringing a tapered crimping portion of the protruding portion having a width at its tip end wider than the hole portion into contact with a longitudinal edge of the hole portion to raise the crimping portion and position the tip end of the crimping portion within the first relief portion, and crimping the hole portion so that the crimping portion expands the hole portion in the width direction; and a molding process for forming the other portion into a target shape.

[11] The joining method according to the above item

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

[12] In the above

[10] or

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

[13] In 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 overlapping members with the punch.

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

[13] above. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic perspective view showing a joint portion of a joint member according to one embodiment of the present invention. [Figure 2] FIG. 2 is a side view of the joint according to the embodiment. [Figure 3] FIG. 2 is a top view of the joint according to the embodiment. [Figure 4] FIG. 2 is a schematic perspective view of a joining portion for explaining the joining method according to the embodiment. [Figure 5] 5 is a cross-sectional view taken along line XX in FIG. 4, illustrating a central cross section in the width direction of a joint portion for explaining the joining method according to the embodiment. [Figure 6] FIG. 4 is a top view of the joint portion of the first member according to the embodiment before joining. [Figure 7] FIG. 4 is a top view of a joint portion of a second member according to the embodiment. [Figure 8] FIG. 4 is a schematic top view showing the positional relationship between the protrusion and the hole according to the embodiment. [Figure 9] FIG. 10 is a schematic perspective view showing a joint portion of a joint member according to another embodiment of the present invention. [Figure 10] FIG. 2 is a schematic perspective view showing a press-formed member as an example of the joining member according to the embodiment. [Figure 11] 2A to 2C are schematic cross-sectional views showing the configuration and movement of a die for forming the press-formed member according to the embodiment. [Figure 12] FIG. 2 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. [Figure 13] FIG. 10 is a schematic perspective view showing another example of a press-formed member. [Figure 14] FIG. 2 is a schematic perspective view showing one flow of a manufacturing process for the press-molded member. [Figure 15] 5A to 5C are schematic perspective views showing another flow of the manufacturing process of the press-molded member. [Figure 16] FIG. 10 is a schematic perspective view showing another example of a press-formed member. [Figure 17] FIG. 1 is a schematic perspective view showing a conventional press-formed member. DETAILED DESCRIPTION OF THE INVENTION

[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, the subject is a member in which two plate-shaped workpieces are joined, and the following description focuses on the joint. Therefore, the workpieces may be flat plate-shaped or may be molded structural members having a three-dimensional shape. There are no particular limitations on the shape.

[0020] (jointing material) 1 to 3 show an example of a joint portion of a joint 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 joint portion 110 of the joint 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. Here, the protrusion 12 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 connection portion 13. The direction in which the protruding portion 12 extends from the connecting portion 13 is defined as the longitudinal direction L, and the direction in the plane of the protruding portion 12 and perpendicular to the longitudinal direction L is defined as the width direction W. The hole portion 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 protruding portion 12 when it is superimposed on the first member 1. In this embodiment, the protruding portion 12 is provided in the plane of the first member 1 and is surrounded by a frame portion 11 of the other portion. Furthermore, the hole portion 21 is surrounded by a frame portion 22 of the second member 2 that forms each side of the hole portion 21.

[0021] As shown in FIG. 8, the length L1 of the protrusion 12 before joining is longer than the length L2 of the hole 21. Furthermore, in the joined state, the protrusion 12 has a convex bent portion 12A and a concave bent portion 12B and a crimped portion 12C. The convex bent portion 12A is, for example, connected to the frame portion 11 at a connection portion 13 and extends, and is formed by being bent in the direction of the second member while contacting one edge of the hole 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 21. The convex bent portion 12A and the concave bent portion 12B may be continuous curved surfaces, 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 bend portion 12B 1B Both are narrower than the width W2 of the hole 21. The crimping portion 12C is connected to and extends from the concave bent portion 12B, and its width increases toward the tip in the longitudinal direction L. 1CThe protrusion 12 has a tapered shape with a width greater than the width W2 of the hole. The crimping portion 12C is in contact with the other edge of the hole 21 in the longitudinal direction L and crimps the edges of the hole 21 in the width direction W to spread them apart, thereby joining the first member 1 and the second member 2. The length L1 of the protrusion 12 is approximately equal to the length of the line along the curved surface from the connection portion 13 of the protrusion 12 to the tip of the crimping portion 12C after joining.

[0022] (Joining method) A joining method according to a 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 of the widthwise center taken along the line XX, respectively, showing a state in which a first member 1 and a second member 2 are superimposed, from (a) a state before joining to (c) a state in which 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, etc., 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 1A =W 1B Furthermore, the protrusion 12 extends from the parallel portion 12D and widens toward the tip, with a width W 1C The tapered portion 12C has a width greater than the width W2 of the hole.

[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 protrusion 12 is arranged so that 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. A positioning pin or the like may be used to improve the positioning accuracy of the overlapping.

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

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

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

[0028] Second Embodiment This embodiment is a press forming method using the so-called patchwork method, in which two flat blanks (components) are integrally formed using a single die, and a press forming die to achieve this. The difference from conventional press forming is that the blanks are set in the die without being joined, and are joined at the same time as they are formed.

[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 , the press-formed member 100 will be described as an example, in which 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 between 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] (Press molding method) First, as shown in Figure 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 standard methods such as pins and holes, and are set so that the joints of each blank are aligned correctly in 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 and 123 and the flange portion 115, thereby forming the target shape.

[0034] (mechanical joining) Next, the joining of the two blanks will be explained. In this embodiment, the blanks are mechanically joined together by the movement of the mold during press forming. In this embodiment, the description will be focused 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 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 overlapped. 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] 12 is a schematic enlarged cross-sectional view showing the behavior of the dies 3, 4 and the blanks 1A, 2A in the vicinity of the joint 110 shown in cross section along the line XX in FIG. 4. The joint of the pad 32, which becomes the upper die 3, has a convex pressing portion 32A and a concave first relief portion 32B adjacent to the pressing portion 32A. The joint of the punch 41, which becomes the lower die 4, has a concave second relief portion 41A.

[0037] After setting the blanks 1 and 2 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 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 longitudinal edge of the hole 21, and that the convexly bent portion 12A bends 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 the second blank. 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 contacting the lower die 4. Furthermore, when the crimped portion 12C rises, the first relief portion 32B of the pad 32 prevents the tip of the crimped portion 12C from contacting 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 has been 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 pressing 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 pressing 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 is a method for joining press-formed members by mechanically joining members having a U-shaped cross section consisting of a top plate and vertical wall portions, or a hat-shaped cross section consisting of a top plate, vertical wall portions, and flange portions. For example, as shown in Fig. 10, a press-formed member 100 will be described, in which a first member 1 having a hat-shaped cross section and a second member 2 having a U-shaped cross section are stacked inside the first member 1 and joined at the center of the top plate portions 113 and 122.

[0044] FIG. 14 is a schematic perspective view showing a flow of a 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 in a location corresponding to the joining portion 110 of the first blank 1A (FIG. 14(a)). Then, a rectangular hole 21 is formed in a location corresponding to the joining portion 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 processing of the protrusion 12 on the first blank 1A and the processing of the rectangular hole 21 on the second blank 2A in the blank processing step are not limited to shearing, laser processing, electric discharge processing, 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 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, the press forming method can be bending, drawing, or the like, and is not particularly limited.

[0046] In the subsequent joining process, first, the first member 1 and the second member 2 are 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. 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. As such, 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. FIGS. 4(a) to 4(c) show perspective views of the joining portion from an unjoined state to the completed joining state. FIG. 12 shows a schematic cross-sectional view of the joining portion taken along line XX 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 comes into contact with the parallel portion 12D of the protrusion 12, as shown in FIG. 12(a). Then, as the pad 32 descends, the pressing portion 32A is inserted into the hole 21, as shown in FIG. 12(b). The parallel portion 12D of the protrusion 12 is then bent and deformed. Of parallel portion 12D, a first portion extending from connection portion 13 with another portion of first member 1 is bent toward second member 2 to form convexly bent portion 12A. At this time, it is preferable that the connection portion 13 side of parallel portion 12D is left a predetermined amount beyond one edge of hole 21 in the longitudinal direction, and convexly bent portion 12A is bent 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 forms an angle with respect 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 crimping 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 crimping portion 12C and the upper die 3.

[0049] 12(c), when pad 32 continues to be pressed in, crimping portion 12C is inserted into hole 21. 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. In this way, two members 1 and 2 are joined.

[0050] (Fourth embodiment) As explained 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 machined in advance 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 a flow of a manufacturing process for a press-formed member 100 according to the second embodiment. In the blanking process, the outer peripheries of a first blank 1A and a second blank 2A are processed into a blank shape (FIGS. 15(a) and 15(b)). Next, in the forming process, 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 a first member 1 (FIG. 15(c)). Then, the second blank 2A is 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 a second member 2 (FIG. 15(d)). Next, in the example of FIG. 7, a protrusion 12 is formed in 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 are all 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 Fig. 16, a press-formed member according to a fifth embodiment can also be made in which two hat-shaped cross-section members 1 and 2 are joined together at flange portions 115 and 124.

[0053] (Sixth embodiment) Furthermore, the joining method described above is intended to join the first member 1 and the second member 2 at a certain point inside them, but it may also be possible to join the first member 1 and the second member 2 at an end of the first member 1 as shown in Fig. 9. In that case, the protrusion 12 is processed to protrude from the end of the first member 1.

[0054] (Other conditions) The present invention is intended for use as a temporary joint to hold components together before the final welding process. Therefore, it is sufficient to have a bonding strength sufficient to prevent the components from separating after temporary joining. If the bonding strength is insufficient, the number of joints can be increased.

[0055] In the above example, the protrusion is approximately rectangular, and the hole is rectangular. Regarding the relative dimensional relationship between the protrusion and the hole, the length L1 of the protrusion is greater than the length L2 of the hole, and the width W of the convex and concave bends is 1A , W 1B is narrower than the width W2 of the hole, and the maximum width W of the crimped part 1C must be wider than the width W2 of the hole. The length L1 of the protrusion is approximately equal to the line length along the curved surface from the connection point 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 is applicable to steel plates with a tensile strength of 270 to 1800 MPa and a thickness of 0.7 to 2.3 mm. The dimensions of the protrusion are length L1 x maximum width W 1C The dimensions of the hole can be 10-50mm x 5-50mm (length L2 x width W2), and 7-35mm x 5-50mm (length L2 x width W2). The taper opening angle φ of the crimped portion can be 0.5-10°. 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 of manufacturing joining member> The joining method according to the above embodiment includes a joining step of joining a first member 1 and a second member 2, and can be used as a manufacturing method for a joined 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 joined. This manufacturing method for the joined member 100 may also include a welding step. It may also include a step of applying an adhesive before the joining step. In this case, the mechanical joining according to the above embodiment may be used to cure the adhesive bonded members. [Industrial Applicability]

[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. [Explanation of symbols]

[0058] 100 Joining members (press-formed members) 110 (mechanical) joints 111 (welded) joints 1 First member 1A First blank (main body part) 1B First member (main body part) 11 Frame 12 Protrusion 12A Convex bent part 12B Concave bend 12C Crimping part (tapered) 12D parallel section 13 Connection 113 (Main body part) Top plate 114 (Main body part) Vertical wall 115 Flange 2 Second member 2A Second blank (reinforcement part) 2B Second member (reinforcement part) 21 Hole 22 Frame 122 (Reinforcement parts) Top plate 123 (reinforcement part) vertical wall 124 (reinforcement part) flange part 3 Upper mold 31 Die 32 pads 32A Push part 32B (first) relief 4 Lower mold 41 Punch 41A (second) relief part

Claims

1. A joined member in which a first member having a protrusion and a second member having a hole are overlapped and joined in a plate thickness direction, The protrusion has a length longer than the hole before joining, The protrusion is a convex bent portion having a width narrower than that of the hole portion, connected to another portion of the first member, extending, and bent toward the second member; a concave bending portion having a width narrower than that of the hole portion, connected to and extending from the convex bending portion, and bent in the opposite direction to the convex bending portion, and inserted into the hole portion; a crimping portion that is connected to the concave bent portion, extends, and has a tapered shape that widens toward its tip, the tip being wider than the hole portion, and crimps the hole portion so as to widen it; A joining member having the above structure.

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

3. The joining 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-molding die for press-molding the joining member according to claim 2 or 3, 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 is provided to join two blanks at a location corresponding to the flat portion of the member, The joint portion is a press molding die having 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 second escape portion provided on the other die, into which the convex push-in portion is inserted.

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

6. The press molding die according to claim 4 , 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 a plate thickness direction, The length of the protrusion before joining is longer than the length of the hole, a first portion of the protrusion, which is connected to and extends from another portion of the first member and has a width narrower than that of the hole, is bent toward the second member to form a convex bent portion; a second portion of the protrusion, which is connected to and extends from the convex bent portion and has a width narrower than that of the hole portion, is bent in the opposite direction to the convex bent portion and inserted into the hole portion to form a concave bent portion; A joining method in which a tapered portion that is connected to the concave bent portion and extends while widening toward the tip, and whose tip is wider than the hole portion, is crimped to expand the hole portion, thereby forming a crimped portion.

8. 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, by press forming. 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; The joining method according to claim 7 , further comprising: 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 to at least one of the top plate portion and the flange portion.

10. 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 stacked in a plate thickness direction to be integrally molded, and 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 is molded, and the first member and the second member are joined by press molding at a location corresponding to the flat portion, A press molding die having a joining portion including a convex push-in portion and a concave first relief portion adjacent to the push-in portion, which is provided on one of a pair of opposing dies, and a concave second relief portion, which is provided on the other die and into which the convex push-in portion is inserted, is used, a portion of the protruding portion of the first member that is connected to another portion of the first member and extends and has a width narrower than the hole portion is pushed into the hole portion and the second relief portion by the pushing portion; a joining process in which a tapered crimping portion of the protrusion, the tip of which is wider than the hole, is brought into contact with an edge of the hole in a longitudinal direction, thereby raising the crimping portion and arranging the tip of the crimping portion within the first relief portion, and the crimping portion crimps the hole so as to expand the hole in a width direction; a molding process for molding other portions into a target shape; The bonding method according to claim 7, comprising:

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

12. 11. The joining method according to claim 10, wherein the pair of opposing dies is a pad and a punch, and the pad is lowered to clamp and press the overlapped members with the punch to join them.

13. The joining method according to claim 10, wherein the pair of opposing dies is a die and a punch, and the die is lowered to clamp and join the overlapping 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 claims 7 to 13.

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