WO2006004084A1

WO2006004084A1 - Fastening member for press-fit joining and press-fit joining structure of the same

Info

Publication number: WO2006004084A1
Application number: PCT/JP2005/012323
Authority: WO
Inventors: Akira Masuda; Akira Nozue; Osamu Kimpara
Original assignee: Ohashi Technica, Inc.
Priority date: 2004-07-05
Filing date: 2005-07-04
Publication date: 2006-01-12
Also published as: KR20060086400A; KR100785550B1

Abstract

A fastening member for press-fit joining and a press-fit joining structure of the fastening member that are used to join element plates, structural members, brackets, etc. forming a vehicle, machine, etc., that provide easy and good joining to achieve excellent joining strength, and that are economically superior. A fastening member has a projection (6) projecting, together with a screw section (4), from a base section (3) and formed in a diameter larger than that of the screw section (4). The projection (6) is solid-state welded to a hole section (10), provided in a plate member (8), by press-fit that involves electric resistance heat. The projection (6) has a cross-sectional shape homothetic to the hole section (10) and has a predetermined press-fit interference (d).

Description

Specification

Fastening member for press fitting and its press fitting structure

Technical field

TECHNICAL FIELD [0001] The present invention relates to a press-fit joining nut, a flanged nut, a fastening member such as a bolt, and the press-fit joining structure used for joining element panels, structural members, brackets and the like constituting vehicles, machines and the like.

Background art

Conventionally, when welding a nut or flanged nut for joining other members to a steel plate, a so-called projection welding method or arc welding method has been used. In this projection welding method, as shown in FIG. 26, a plurality of protrusions 102 are provided on the back surface of the nut 100, while a hole 106 is provided in the steel plate 104, and the protrusion of the nut 100 is provided on the plate 104. The portion 102 is pressed and energized therebetween to melt the projection 102 and the plate 104, and the nut 100 is welded to the surface of the plate 104. Patent Documents 1 and 2 also describe projection welding. Patent Document 3 has a description regarding press-fit bonding.

[0003] When welding bolts for joining other members to a steel panel, a so-called projection welding method or arc welding method has been used. In welding using this projection welding method, for example, there is a welding bolt disclosed in Patent Document 4, which, as shown in FIG. 27, is near the periphery of the seating surface of the head 111 of the bolt 110 for welding. The welding convex portion 112 is provided on the peripheral surface of the seating surface, and the stepped portion 114 is provided concentrically on the peripheral portion of the seating surface. Then, the bolt hole 117 provided on the panel 116 of the automobile is passed through the shaft 113 of the bolt 110 and positioned at the center, and a welding current is passed between the welding convex part 112 and the panel 116 in contact with the bolt 116. Weld 110.

[0004] Also, Patent Document 5 describes a welding bolt in which several welding projections are provided on the periphery of the bolt head, which is an annular ring surrounding a screw rod on the seat surface of the bolt head. Protrusions are formed, and the annular protrusions form a partition between the metal plate and the bolt head seat side to form a seal structure. Patent Document 1: Japanese Patent Application Laid-Open No. 55-40052

Patent Document 2: Japanese Utility Model Publication No. 6-86876

Patent Document 3: Japanese Patent Laid-Open No. 2001-353628

Patent Document 4: Japanese Utility Model Publication No. 5-47521

Patent Document 5: Japanese Patent Laid-Open No. 5-318135

[0006] As shown in Fig. 26 (b), the projection welding is performed by melting the portions of the protrusion 102 and the plate 104, and in this case, the melting is uneven and welding is performed. There are problems such as the strength is not constant and the nut falls down during welding. Further, the surface of the plate may not be satisfactorily welded by projection due to the acid coating 108 or the like. In particular, in the case of a high-strength steel plate, there are many alloy elements such as Si, Ti, Nb, etc., so that a large amount of oxide film 108 is generated on the surface, and this oxide film becomes an insulation resistance. As a result, the current flows and becomes difficult to weld, and at the same time, the spatter of the melted portion sparks and scatters during welding, resulting in very high spatter. It can also cause environmental problems.

In the case of projection joining, as shown in FIGS. 26 (b) and 26 (c), since the protrusions 102 of the nut 100 are pressed and melted to the plate 104, the plate of the plate 104 is melted and deformed. If this is not the case, the new surface will be difficult to come out, so that the acid coating 108 on the plate 104 side may remain, and there is a problem that the strength of the joint cannot be sufficiently obtained. In addition, the high-strength steel plate is hard and has a large deformation resistance, so that there is a problem that << the projection 102 of the nut cannot be joined well to the steel plate constituting the plate 104.

In the projection welding shown in FIG. 27, the weld convex 112 is melted and welded to the panel 116. In this case, the weld strength is low, and the joint accuracy is further improved. There is a problem that it is difficult to improve accuracy because it depends on the bonding state of the part. At the time of projection welding, the melted part of the joint sparks and scatters (sputtering), and this spatter adheres to the screw shaft of the bolt and causes screw failure, and oxide is deposited on the welded part. It has become a cause of deterioration of strength, poor welding, or bad working environment. In addition, the dimensional accuracy of the weld convex 112 and the step 114 There is a risk that the current distribution during welding may not be constant due to variations in welding, welding accuracy, etc., and welding may become unstable.In addition, it is required that the stepped portion 114 completely closes the bolt hole 117 with high accuracy. It is not easy to ensure airtightness. In welding with the above-mentioned annular protrusion, welding work is difficult, and the sealing performance of the annular protrusion depends on the welding accuracy of the bolt, the accuracy of the panel surface and the seating surface of the bolt, and ensures a stable sealing performance. Has a problem.

[0009] Further, in the process bonding, as shown in Fig. 27 (b), when the oxide film 118 is formed on the surface of the panel 116, the projection welding is hindered, and as shown in Fig. 27 (c). In addition, when the welding projection 112 of the bolt 110 is pressed and welded to the panel 116, the new surface is difficult to come out if the plate of the panel 116 is not melted and deformed. Therefore, the oxide film 118 on the panel 116 side remains, There is a problem that the strength of the joint cannot be obtained sufficiently. In particular, when the panel is a high-strength steel plate, welding becomes difficult and at the same time, the number of spatters generated during welding becomes very large, which poses danger to the worker and deteriorates the working environment.

[0010] The present invention has been made to solve the above-described problems, and is a fastening member for press-fit joining that is easily and satisfactorily joined, has excellent joint strength, and is economical. An object is to provide a joint structure.

Disclosure of the invention

In order to solve the above technical problem, the fastening member for press-fitting and joining according to the present invention has a diameter larger than that of the parenthesis screw part from the base part together with the screw part as shown in FIGS. Protrusions that are solid-phase bonded by press-fitting with electrical resistance heat into holes provided in the plate material, and have protrusions with a predetermined press-fitting allowance formed by forming a cross-section similar to the hole in the bracket It is. Here, the fastening member includes a nut, a bolt, and the like, and in the case where the projecting portion is a bolt, a diameter-enlarged portion formed between the head portion and the shaft portion corresponds.

[0012] Further, as shown in FIGS. 11, 17, and 24, the press-fitting structure according to the present invention includes a plate member provided with a hole at a predetermined position, and the protruding portion bonded to the hole. In the joining structure with the fastening member, the plate member is held by one electrode, while the fastening member is held by another electrode, and an electric resistance heat is applied to both joining portions by energizing both the members. In addition to being generated, the two members are bonded together while forming a bonding interface by press-fitting, and the bonding of the brackets is a solid-phase bonding. As shown in FIG. 1, the nut for press-fitting and joining according to the present invention is formed to protrude in a cylindrical shape from a base portion, a screw hole penetrating the central portion of the base portion, and a peripheral portion of the screw hole, This is a structure having a protrusion portion provided with a predetermined press-fitting allowance by being solid-phase bonded to a hole portion provided in the plate by press-fitting with electric resistance heat and forming a cross-section having a similar shape to the parenthesis hole portion.

[0014] The nut for press-fitting and joining according to the present invention has a configuration in which a burr storage portion is formed on the back surface of the base portion so as to surround the protruding portion and also has an annular groove portion force.

[0015] As shown in FIG. 13, the press-fit joining nut according to the present invention is formed integrally with a base portion having a screw hole at the center portion and a base portion on the back surface side of the base portion, and the above-mentioned at the center. A flange portion provided with a hole portion continuous with the screw hole, and a peripheral force around the hole portion of the flange portion are formed in a cylindrical shape, and solid phase is formed by press fitting with electric resistance heat into the hole portion provided in the plate. And a projection having a predetermined press-fitting allowance formed by forming a cross-section having a similar shape to the hole of the parenthesis.

[0016] In addition, the nut for press-fit joining according to the present invention has a configuration in which a groove-shaped groove storage portion surrounding the protruding portion is provided on the back surface portion of the flange portion.

[0017] The nut for press-fitting and joining according to the present invention has a plate thickness of the outer end portion of the flange portion of 1.

The entire seating surface on the back surface of the flange portion is formed in a concave spherical shape.

[0018] Further, as shown in FIGS. 1 and 13, the nut for press-fitting and joining according to the present invention has a tube thickness (s) of 1. Omm or more, as shown in FIGS. The height width (h) ranges from 0.5 mm to 2. Omm.

[0019] As shown in FIGS. 11 and 17, the press-fitting structure according to the present invention includes any one of the above press-fitting joints having a plate provided with a hole at a predetermined position and a protrusion joined to the hole. The above-mentioned nut is held by one electrode, while the above-mentioned nut for press-fitting is held by another electrode. In addition to generating gas resistance heat, it is joined while forming a joining interface between the two members by press fitting, and the joining of the parenthesis is a solid state joining.

[0020] The press-fitting structure according to the present invention is a structure using a high-tensile steel material or a surface-treated steel material for the plate. Furthermore, the press-fit joint structure according to the present invention is shown in FIGS. Thus, the protrusion height width (h) of the protrusion is the same as or smaller than the plate thickness (t) of the plate.

[0021] As shown in FIG. 20, the bolt for press-fitting and joining according to the present invention is a bolt having a head portion and a shaft portion provided with a screw groove, and between the head portion and the shaft portion, An enlarged diameter portion having a diameter larger than that of the shaft portion is formed, a predetermined press-fitting allowance is provided between the hole portion provided in the panel and the enlarged diameter portion. In this configuration, the diameter portion is solid-phase bonded to the hole portion.

[0022] Further, the press-fitting bolt according to the present invention is formed such that the diameter of the enlarged diameter part is larger than the diameter of the shaft part by 1 mm or more, and the height of the enlarged diameter part is about 1 mm to 5 mm. This is a range configuration.

[0023] The press-fitting and joining bolt according to the present invention has a configuration in which a groove-shaped burr storage portion surrounding the enlarged-diameter portion is provided on the back surface portion of the head portion.

[0024] Further, the press-fitting bolt according to the present invention has a configuration in which a high-tensile steel material is used as a constituent material.

[0025] As shown in FIG. 24, the press-fitting structure according to the present invention is a panel for press-fitting that has a panel provided with a hole at a predetermined position and the enlarged-diameter part bonded to the hole. The above-mentioned panel is held by one electrode while the above-mentioned press-fitting bolt is held by another electrode, and an electric resistance heat is applied between the two members by energizing both the members. In addition, the two members are joined together while forming a joining interface by press-fitting, and the parenthesis joining is a solid-phase joining.

[0026] In addition, the press-fit joint structure according to the present invention has a structure in which the height width (h) of the enlarged-diameter portion is equal to or smaller than the plate thickness (t) of the panel, as shown in FIG. It is.

[0027] The press-fitting structure according to the present invention is a structure using a high-strength steel material or a surface-treated steel material for the panel.

[Effect of the Invention]

According to the fastening member for press-fit joining according to the present invention, it is formed to protrude from the base together with the screw part to have a larger diameter than the screw part of the bracket, and is solid-phase joined by press-fitting with electric resistance heat in the hole provided in the plate member. Since it has a structure with protrusions, it can be done quickly with only a simple process of press-fitting and energization. Bonding can be performed quickly and manufacturing is easy and economical. In addition, the bonding interface is cleaned, bonding is performed well, and the strength is excellent. Further, in this solid-phase bonding by press-fitting, since almost no spatter is seen, there is an effect that a good working environment is maintained and workability is excellent.

[0029] The press-fit joining structure according to the present invention is a joining structure of a plate member provided with a hole at a predetermined position and the above-described fastening member joined to the hole. To generate electrical resistance heat at the joints between the two, and the brace joint is made into a solid state joint. In addition, there is an effect that the bonding interface is cleaned, the bonding is performed well, and a bonding structure excellent in strength can be obtained. Furthermore, since this press-fit joining is a solid-phase joining, there is almost no spatter generated during projection welding, so that a good working environment is maintained and workability is excellent.

[0030] According to the nut for press-fitting and joining according to the present invention, a base portion, a screw hole penetrating through the central portion of the base portion, and a cylindrical protrusion projecting from the screw hole and press-fitted into a hole portion provided in the plate Because it has a structure that has a solid-phase-bonded protrusion, it can be quickly bonded with a simple process of only press-fitting and energization, making it easy to manufacture and economical, and the bonding interface is cleaned and bonded. Is carried out well and has an excellent effect in terms of strength. Furthermore, solid phase bonding by press-fitting has the effect of maintaining a good working environment and excellent workability because almost no spatter is observed.

[0031] Further, according to the press-fit joining nut according to the present invention, since the burr storage portion is provided, the burr generated by the press-fitting is stored in this nose storage portion, whereby the back surface of the nut is pre-treated. There is an effect that a high-quality bonded structure part can be obtained by being in close contact with the surface of the sheet.

[0032] According to the press-fit joining nut according to the present invention, the flange portion formed on the back surface side of the base portion, and the flange portion force is formed in a cylindrical shape and is solid-phase bonded to the hole provided in the plate. Because it has a structure that has a protruding part that can be pressed, it can be joined quickly and easily by simple steps of press-fitting and energization, and it is easy to manufacture and is economical. There is also an excellent effect. In addition, since the bearing surface of the nut with flange is in close contact with the plate, high load capacity can be demonstrated and a wide seating surface can be secured. The torsion and the like are reliably reinforced, the screw can be prevented from loosening during long-term use, and the surface can be prevented from being bitten by a minute lateral movement applied to the joint.

[0033] Further, according to the nut for press-fitting and joining according to the present invention, since the groove-shaped groove storage portion surrounding the projecting portion is provided on the back surface portion of the flange portion, it is generated by being cut by press-fitting. The burr is housed in this barrier housing, and the back surface of the flanged nut is more firmly attached to the surface of the plate, so that it is possible to obtain a good quality, joined structure part.

[0034] Further, according to the nut for press-fitting according to the present invention, the plate thickness of the outer end portion of the flange portion is about 1. Omm, and the entire seating surface is formed in a concave spherical shape. Heat generation allows the flange surface to conform to the shape of the plate, and even if the plate is slightly bent, pressure can be applied relatively evenly, and the pressure on the outer periphery is strong and prevents loosening. There is an effect that.

[0035] Further, according to the press-fit joining nut according to the present invention, the wall thickness of the projecting portion is formed to be not less than 1. Omm, and the projecting height width of the projecting portion of the bracket is from 0.5 mm to 2. Since it is configured in the range of about Omm, an excellent effect in strength can be obtained.

[0036] According to the press-fitting structure according to the present invention, electricity is passed between the plate provided with the hole and the press-fitting nut, and electric resistance heat is generated at the joint portion between the two, and the press-fitting is performed. As a result, the joint interface between the two parts is a solid-phase structure, so that it is possible to perform quick joining with a simple process of only press-fitting and energization, and the degree of freedom in joining conditions is easy to manufacture. It is economical and has an effect that the bonding interface is cleaned and the bonding is performed well, and a bonding structure having excellent strength can be obtained. Furthermore, since this press-fit joining is a solid-phase joining, almost no spatter generated during projection welding is observed, so that a good working environment is maintained and workability is excellent.

[0037] Further, according to the press-fit joining structure according to the present invention, even if a structure using a high-strength steel material or a surface-treated steel material for the plate is used, good joining can be performed without being affected by the oxide film, and the high-tensile steel material can be obtained. Combined with the strength of the steel, a joint structure with excellent strength can be obtained, and even if the steel material is surface-treated, the surface treatment material does not enter the joint, so that the surface treatment is the same as in conventional projection welding. Excellent strength can be secured without being affected by the above.

[0038] Further, according to the press-fitting structure according to the present invention, the protrusion height width of the protrusion is set to the plate plate. Since the structure is the same as or smaller than the thickness, a good bonding interface is formed and excellent bonding strength is obtained, and the protruding part protrudes from the plate, which may cause inconvenience in assembling other parts. Absent.

[0039] According to the press-fitting bolt according to the present invention, an enlarged portion having a diameter larger than that of the shaft portion is formed between the head portion and the shaft portion. A predetermined press-fitting allowance is provided between the expanded diameter part, and a solid-phase joining is performed by applying current between them and press-fitting with electrical resistance heat. Therefore, it is easy to manufacture and economical, and the bonding interface is cleaned and the bonding is performed well, and the strength is excellent. In addition, the solid phase bonding by press-fitting has an effect that a good working environment is maintained and workability is excellent because sputtering hardly occurs.

[0040] Further, according to the bolt for press-fitting according to the present invention, the diameter of the enlarged diameter part is formed to be 1 mm or more larger than the diameter of the shaft part, and the height width of the enlarged diameter part is in the range of about 1 mm to 5 mm. As a result, it is possible to obtain an excellent strength effect.

[0041] Further, according to the press-fitting bolt according to the present invention, since the groove-shaped groove storage portion surrounding the enlarged-diameter portion is provided on the back surface portion of the head portion, it is generated by being cut by press-fitting. The burr is housed in the burr storage section, so that the back surface of the bolt adheres to the surface of the panel, and a high-quality bonded structure part can be obtained.

[0042] Further, according to the bolt for press-fitting according to the present invention, even if a configuration using a high-strength steel material is used as a constituent material, the same high-strength joining as a mild steel material can be performed, and the joint portion does not melt, so that high tension Hydrogen does not penetrate into steel bolts, and troubles caused by hydrogen in steel such as delayed fracture, stress fracture, and hydrogen embrittlement are released, and there is an effect that high-tensile materials can be used with confidence.

[0043] According to the press-fit joint structure according to the present invention, the panel is provided with a hole provided at a predetermined position and the press-fit joint bolt joined to the hole, and the press-fit joint structure Bonding is performed while forming a bonding interface between the two members, and the structure of the parenthesis bonding is a solid-phase bonding structure, so that the bonding can be performed quickly with a simple process of only press-fitting and energization, and manufacturing is easy and economical. In addition, there is an effect that the bonding interface is cleaned, the bonding is performed well, and a bonding structure excellent in strength can be obtained. In addition, this solid-state bonding by press-fitting is As in the case of Chillon welding, the temperature of the material at the joint increases rapidly and does not scatter so as to melt and explode. Therefore, almost no spatter is generated, so that a good working environment is maintained and workability is excellent. There is.

[0044] Further, according to the press-fit bonding structure according to the present invention, the height width of the enlarged diameter portion is formed to be equal to or smaller than the plate thickness of the panel, so that a good bonding interface is formed and excellent bonding is achieved. Strength is obtained, and the panel force enlarged diameter part protrudes and does not cause any inconvenience when assembling other parts.

[0045] The press-fit joint structure according to the present invention is a structure using a high-strength steel material or a surface-treated steel material for the panel, and can perform good joints without being affected by the oxide film, and can provide a high-strength steel plate. Combined with the strength of the steel, a strong joint structure can be obtained, and even if the steel is surface-treated, the surface-treated material does not enter the joint, so the effect of the surface treatment is different from that of conventional projection welding. Excellent strength can be secured without receiving.

Brief Description of Drawings

[0046] [FIG. 1] (a) is a side view, (b) is a cross-sectional view, and (c) is a side view of a plate according to a first embodiment of the present invention.

FIG. 2 relates to the embodiment, (a) of the other nut is a partial sectional view of the side, and (b) is a plan view.

FIG. 3 is a diagram showing various forms (a) and (b) of a burr storage section according to the embodiment.

FIG. 4 relates to the embodiment of the present invention, (a) is an explanatory view of a press-fitted state, and (b) is a bottom view of the nut.

FIG. 5 is a diagram showing a measurement result of in-house test A according to the embodiment.

FIG. 6 is a diagram showing measurement results of in-house test B according to the embodiment.

FIG. 7 is a diagram showing measurement results of other in-house tests according to the embodiment.

[Fig. 8] A graph showing the results of in-house test peel strength measurements, where (a) is a SPCC steel plate, (b) is a 780 MPa steel plate, and (c) is a 980 MPa steel plate.

[Fig. 9] A table summarizing the peel strength results from in-house tests.

[Fig. 10] A graph showing the measurement results of peel strength when a steel plate is used for the plate in an in-house test. FIG. 11 is a diagram for explaining an application of the press-fit joint structure according to the embodiment.

[FIG. 12] relates to another embodiment, (a) is an explanatory view of a press-fitted state, and (b) is a bottom view of the nut.

FIG. 13 (a) is a side view, (b) is a cross-sectional view, and (c) is a side view of a plate of a flanged nut according to a second embodiment of the present invention.

[Fig. 14] (a) is a side sectional view of a flanged nut according to another embodiment, and (b) is a plan view.

FIG. 15 is a diagram showing various forms (a) and (b) of the burr storage section according to the embodiment.

FIG. 16 relates to the embodiment, (a) is an explanatory view of a press-fitted state, and (b) is a bottom view of the nut.

FIG. 17 is a diagram for explaining an application of the press-fit joint structure according to the embodiment.

FIG. 18 is a cross-sectional view of a nut having a flange portion of another form according to the embodiment.

[Fig. 19] relates to another embodiment, (a) is an explanatory view of the press-fitted state, and (b) is a bottom view of the nut.

FIG. 20 is a side view of a bolt according to a third embodiment of the present invention, and FIG. 20 (b) is a side view of the panel.

FIG. 21 relates to the embodiment, (a) of the other bolts is a side sectional view, and (b) is a plan view.

FIG. 22 is a diagram showing various forms (a) and (b) of the burr storage section according to the embodiment.

FIG. 23 relates to an embodiment of the present invention, in which (a) is an explanatory view of a press-fitted state, and (b) is a bottom view of the bolt.

FIG. 24 is a diagram for explaining a use of the press-fit joint structure according to the embodiment.

FIG. 25 relates to another embodiment, (a) is an explanatory view of a press-fitted state, and (b) is a bottom view of the bolt.

FIG. 26 relates to the conventional example, (a) is an explanatory view of the projection welding method, (b) is a partially enlarged view before welding, and (c) is a partially enlarged view after welding.

FIG. 27 relates to a conventional example, (a) is an explanatory view of a welding bolt of an automobile, (b) is a partial view before welding, and (c) is a partial view after welding.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below. First, according to the first embodiment, a nut as a fastening member for press-fitting and its press-fitting structure will be described with reference to the drawings. FIG. 1 shows the nut 2. The nut 2 includes a base 3 having a hexagonal outer shape, a screw hole 4 penetrating through the center, and a protrusion 6 (inlay part) formed to protrude downward from the periphery of the screw hole of the base 3 in a cylindrical shape. have. The protruding portion 6 has a circular cylindrical shape (annular shape) having a predetermined thickness (s), and a screw hole 4 continuous with the screw hole 4 is formed inside. The protruding portion 6 is formed to protrude downward from the back surface portion 5 of the base portion 3 with a predetermined height width (h).

FIG. 2 shows another form of the press-fitting nut 12. Also on the nut 12, a protrusion 6 is formed downward from the periphery of the screw hole 4 of the base 3, and the back surface 5 of the base 3 has a burr that has an annular groove force in a state of surrounding the protrusion 6. A storage portion 9 is formed. Further, when the nut 12 is molded, the central portion of the upper surface of the base portion 3 is pressed by a press carriage (concave portion 13), and the protruding portion 6 is extruded and formed downward.

[0049] The burr storage section 9 has various forms as shown in FIG. 3, for example, the burr storage section 9 shown in FIG. 3 (a) has a groove provided along the vicinity of the protrusion 6. It is. The burr storage portion 9 shown in FIG. 2B is formed in a tapered shape from the upper end of the groove near the protrusion 6 toward the lower outside, and this is a concave space on the entire back surface of the nut 2. Is formed.

[0050] Regarding the shape of the nut, any type of hexagonal nut can be used, and a square nut can also be used. Other polygonal nuts or round welded nuts with hollows formed at multiple locations around the periphery, polygonal nuts stipulated by JIS, T-shaped welded nuts with welded discs, etc. Any type of nut can be used. By forming the protruding portion 6 on the back surface portion 5 of these nuts, a nut for press-fit joining can be obtained. Polygonal nuts are easy to fix when the nut is threaded (threaded).

[0051] In addition, in the case of a square nut (square, hexagon, etc.), the outer diameter of the protrusion 6 is the same as or smaller than the width of two parallel surfaces of the nut. For the other nuts, the outer diameter of the protruding part is made smaller than the radial size of the base part. If the size of the base portion 3 is within this range, the electrodes can be well placed during energization and press-fitting, and the electrical resistance can be reduced. General projection welding nuts have protrusions on the welds, so the back side of the nut is widened. Therefore, the shape of the nut becomes large. However, in the nut 2 according to this embodiment, in principle, the nut base 3 can be made as small as the size of the protrusion 6 (cross section orthogonal to the axis), and the size and size of the nut 2 can be reduced. Contributes to weight reduction. Nut 2, 12 etc. are made of steel.

[0052] The plate 8 is a high-tensile steel plate that is employed as a structural component such as an automobile chassis. This high-strength steel sheet is a steel sheet containing alloy elements such as C, Si, Ti, Nb, or a dual-phase (DP) steel sheet that has been heat-treated, and has an I-tensile strength of 8 OkgfZmm ² or more. Have. In resistance welding, the effect of the oxide film occurs when the tensile strength is 80 kgfZmm ² or more, and the power of press-fitting according to this embodiment is exhibited.

[0053] A circular hole 10 is formed in the plate 8 at a predetermined position. The hole 10 is a straight hole that is orthogonal to the plate 8 surface. The joint of the plate 8 with the nut 2 is flat. Even if there is some bending in the vicinity of the hole 10 of the plate 8, there is no problem in joining if the degree is slight.

[0054] A chamfered portion 7 is formed on the protruding portion 6 of the nut 2 as shown in FIG. 1 and the like, and the height width of the chamfered portion is about 0.3 mm. The chamfered portion 7 is formed for the convenience of mold forming and is also effective as a guide for press-fitting. Note that the chamfered portion 7 is eroded and there is almost no original shape after press-fitting because there is a predetermined press-fitting allowance. The height width (h) of the protruding portion 6 of the nut 2 is a concept including the chamfered portion 7. The thickness (s) of the protrusion 6 is a dimension between the valley of the screw groove of the screw hole 4 and the outer diameter portion of the protrusion 6.

[0055] Regarding the relationship between the plate thickness (t) of the plate 8 and the height width (h) of the protrusion 6 of the nut 2, the plate thickness (t) is the same as the height width (h). Larger than (t> h, t = h). Conversely, if the height of the nut protrusion 6 is large, the protrusion 6 protrudes from the plate 8 after joining, which may be inconvenient when assembling other parts by bolting.

[0056] With regard to the material of the nut 2 and the plate 8, particularly when the steel nut 2 is connected to the plate 8 made of a high-strength steel plate, the influence of the acid coating is small, and general projection welding is performed. Compared with nut welding, welding defects do not occur, which is preferable. of course , Plate 8 and Nut 2 materials include general steel plates, high-tensile steel plates for automobiles, other metal materials, SUS (stainless steel), a combination of SUS and carbon steel, carbon steel for machine structures, for machine structures Alloy steel, heat-resistant steel, tool steel, panel steel, pig iron, free-cutting steel, bearing steel, steel for general processing, steel for pressure vessels, light metals such as titanium and aluminum are applicable. It can also be applied to high-tensile steel sheets with surface treatment such as zinc plating used in automobiles.

Here, the press-fit joining of the nut 2 to the plate 8 will be described. As shown in FIG. 4, this press-fit connection is to join the protruding portion 6 of the nut 2 to the plate 8 as a base material using a jig having a lower die 14 and an upper die 16 made of chrome copper. The upper die 16 of this jig is provided with a hole 18 in the center for tightly holding the nut 2, and the lower die 14 and the upper die 16 each function as an electrode. The hole portion 18 of the upper mold 16 is in close contact with the upper surface portion and the side surface portion of the nut 2 to reduce electric conduction resistance. In order to prevent contact between the electrodes, the lower end of the hole 18 is positioned slightly above the back surface 5 of the nut. The upper mold 16 can be used without the hole 18.

As shown in FIG. 4, a predetermined press-fitting allowance (d) is formed between the protrusion 6 and the hole 10 of the plate 8. This press-fitting allowance (d) is a dimension with respect to the diameter, and is (dZ2) with respect to the radius. The conditions for press-fitting were an applied current of 22 kA and a pressure of 400 kgf to 450 kgf. The applied pressure is lower than the stress of the base plate (here, the resistance that prevents the nut from entering the plate). Therefore, the press-fitting is started when the applied pressure exceeds the stress reduced by the softness of the plate.

In this press-fitting step, the plate 8 is placed on the upper surface of the lower die 14, while the nut 2 held in the hole 18 of the upper die 16 is lowered together with the upper die 16. Then, the upper die 16 is pressed with a certain pressure applied, and at the same time, electricity is passed between the nut 2 and the plate 8 via the lower die 14 and the upper die 16. Then, as the electric resistance heat is generated, press-fitting of the protruding portion 6 of the nut starts, and the protruding portion 6 moves down in the hole 10 of the plate 8, and the tip of the protruding portion 6 is the hole of the plate 8. Reach the middle position. By such a manufacturing process, a part having a press-fit joint structure including the nut 2 and the plate 8 is obtained. This joint structure is the same as that of the protruding part 6 of the nut 2. The entire periphery is joined to the hole 10 of the plate 8.

[0060] Further, prior to the press-fitting step, it is possible to employ a (preheating pattern) joining method in which a preheating step for preheating the nut 2 and the plate 8 is incorporated. In this preheating process, before starting the above press-fitting, the energization current is kept lower than that at the time of the above-mentioned press-fitting (preheating current of about 1Z2 at the time of press-fitting), and energization is performed with both members in contact with each other. In this preheating process, the upper die 16 is lowered and a preheating current is applied in the same manner as in the press-fitting process. Here, since the purpose is to preheat the nut 2 and the plate 8 as the members to be joined, the temperature of both members is raised so that the joint portion between the two members does not soften. Immediately after this preheating step, the energizing current is increased and the above press-fitting step is started.

In the press-fitting process, the press-fitting of the nut 2 is started as the electric resistance heat is generated, and the projecting portion 6 moves down in the hole 10 of the plate 8. In this case, ironing action occurs at the joint interface between the two members, and press-fitting is performed by a manufacturing process using ironing. Then, press-fitting is performed at a constant pressure and a constant descent rate, and the joint is heated instantaneously, and the back surface 5 of the nut 2 reaches the surface of the plate 8 in a short time, completing the joining. The projecting portion 6 of the nut 2 and the hole portion of the plate are joined together with a solid-phase welding joint interface formed therebetween.

[0062] In solid phase welding, the fact that a clean surface structure is obtained on the joint surface affects the quality of the joint. According to the press-fit welding according to this embodiment, the wall surfaces of the projecting portion of the nut 2 and the hole portion 10 of the plate 8 are slid by the sliding movement at the joint interface. The surface impurity layer is scraped to clean the surface, and the joint becomes a clean structure.

[0063] After that, as the press-fitting proceeds, the joint area of the joint surface portion increases, and conversely, the cross-sectional area difference decreases, so that the current density decreases, and as a result, the generation of resistance heat decreases, and the temperature of the joint surface portion decreases. descend. The joint state by the press-fit joint is the one resulting in solid phase welding accompanied by plastic deformation (thermoplasticity) by press-fit. Then, after the press-fitting is completed, the hardness of the base material of the joint is recovered by cooling, and the joint is firmly joined. Here, in the above press-fit joining, the process of pressurization → energization → press-fit → cooling is followed. Further, the burrs generated by the cutting are stored in the burr storage section 9, whereby the back surface section 5 of the nut 2 is brought into close contact with the surface of the plate 8, and a high quality joint is obtained. A structural part is obtained.

FIG. 5 and FIG. 6 show the test results of the above-mentioned press-fitting in the company. As the plate 8 used here, a high-tensile steel plate (tensile strength 80 kgfZmm ² ) was used. The plate thickness (t) of this plate 8 was 2.8 mm and 1.8 mm. The press-fitting allowance (d) was 0.3 mm with respect to the diameter.

In the in-house test A shown in FIG. 5, the degree of contraction of the inner diameter of the protrusion 6 was measured by changing the protrusion height width (h) of the protrusion 6 of the nut 2. Here, the nut 2 has a size of M8 standard, the outer diameter of the protrusion 6 is 11 mm, and the wall thickness (s) is (11-8) Z2 = 1.5 mm. Fig. 1 (1) shows the measurement of the change in the inner diameter of the protrusion 6 after joining. Judgment was made using a screw plug gauge (CFIS standard) to check whether the nut was screwed in before and after entry, and whether the bolt limit gauge was screwed into the nut after press fitting was checked.

[0066] In the measurement results, (◯) indicates that the gauge can be screwed in without any problem and the inner diameter of the protrusion 6 is not contracted. (△) indicates that although there is a certain amount of resistance, the gauge can be screwed in, and the inner diameter of the protruding portion 6 is slightly contracted. (X) indicates that the gauge could not be screwed in, and that the inner diameter contraction of the protrusion 6 occurred to some extent.

[0067] As a result, the protrusion height width (h) of the protrusion 6 is 0.5 mn! At ~ 1.2mm, plate 8 of any thickness was good (◯). When the protrusion height width (h) was 1.5 mm, the plate 8 of any thickness was good (△). When the protrusion height width (h) was 2 mm, the thickness (t) was 2.8 mm (△), and the 1.8 mm thickness (X). From this, it is considered that the degree of contraction of the inner diameter of the protrusion 6 is generally good when the protrusion height width (h) of the protrusion 6 of the nut 2 is in the range of 0.5 mm to 2. Omm.

[0068] Fig. 2 (2) shows the measurement result of the strength in the in-house test A. The test conditions here were the same as described above, and the bonding strength was measured by changing the protruding height width (h) of the protruding portion 6 of the nut 2. The bond strength was determined by the indentation peel strength (KN) based on JIS standard (B1196).

[0069] As a result, when the protrusion height width (h) of the protrusion 6 is 0.5 mm to 2. Omm, the plate thickness of 2.8 mm is 14.5 to 26.6 KN, and the plate thickness is 1.8 mm. The plate was 8.2-20.1 KN, and good strength was obtained for the plate 8 of any thickness. By the way, JIS standard (B11 The indentation peel strength (KN) of the M8 nut in 96) is 6.03KN. From this, it was confirmed that the protrusion height width (h) of the protrusion 6 of the nut 2 is sufficiently strong and strong within the range of 0.5 mm to 2. Omm.

[0070] Thus, the protrusion height width (h) of the protrusion 6 of the nut 2 is preferably about 0.5 mm or more and about 2 mm or less. If this height width is 2. Omm or more, the bonding strength is deeper than necessary, which is almost the strength level of the base metal, but the amount of burrs is increased. As shown in the test results, if the height width (h) is 0.8 mm or more, a considerable strength is secured, which is preferable. This protrusion height width (h) corresponds to the press-fitting depth at which the protrusion 6 is press-fitted into the hole 10 of the plate 8.

[0071] Fig. 6 shows in-house test B. Fig. 6 (1) shows the degree of contraction of the inner diameter of the protrusion 6 by changing the thickness (s) of the protrusion 6 of the nut 2. The test results are shown. The plate 8 used here is the same as that of the above-mentioned in-house test A. The nut 2 was M8 size, and the press-fit allowance (d) was 0.3mm with respect to the diameter. The protrusion height width (h) of the protrusion 6 was set to 0.8 mm. In this in-house test B, the thickness (s) was changed by changing the outer diameter of the protrusion 6 in the range of 10 mm to 13 mm. At this time, the thickness (s) becomes (outer diameter of the protruding portion−8) Z2. Judgment was made using a thread plug gauge (CFIS standard) as in in-house test A.

[0072] The measurement result of the degree of contraction of the inner diameter was (Δ) for the plate 8 of any thickness when the wall thickness (s) was lmm. In addition, when the wall thickness (s) was 1.5 mm to 2.5 mm, the plate 8 of any plate thickness was good (◯). From this, the thickness (s) of the protruding part 6 of the nut 2 is considered to be generally good in the degree of contraction of the inner diameter of the protruding part 6 within the range of 1. Omm or more.

[0073] Fig. 2 (2) shows the measurement result of the strength in the in-house test B. The test conditions here were the same as in the shrinkage test, and the joint strength was measured by changing the wall thickness (s) of the protrusion 6 of the nut 2. The bonding strength was measured by indentation peel strength (KN) based on JIS standard (B1196).

[0074] As a result, when the thickness (s) of the protrusion 6 is 1.0 mm to 2.5 mm, the plate thickness is 2.8 mm, 15.1 to 23.2 KN, and the plate thickness is 1.8 mm. 8. It was 8 to 12.7 KN, and good strength was obtained for the plate 8 of any thickness. From now on, the protruding part 6 of the nut 2 The wall thickness (s) is lmn! It was confirmed that sufficient and strong strength was secured within the range of ~ 2.5 mm.

Here, the press-fitting allowance (d) between the protruding portion 6 of the nut 2 and the hole 10 of the plate 8 will be described. In the above in-house test, the press-fitting allowance (d) was set to 0.3 mm. This press-fitting allowance (d) is in the range of 0.2 mm to 0.6 mm (preferably 0.3 mm to 0.5 mm) according to internal tests. This press-fitting allowance (d) is a press-fitting allowance with respect to the diameter. When the outer diameter of the protrusion 6 is φ1 and the inner diameter of the hole 10 is φ2, ά = 1-2. In in-house tests, if the press-fitting allowance d is about 0.1 mm, the amount of shaving at the press-fitting allowance is small and the joining is unstable. In addition, when the press-fitting allowance d is 0.6 mm or more, the amount of shrinkage due to the press-fitting allowance increases, resulting in uneven finish.

[0076] In this embodiment, the force that makes the shape of the hole 10 of the plate 8 and the outer shape of the protrusion 6 of the nut 2 circular for ease of processing, etc. If there is a similar relationship, the conditions for press-fitting are satisfied. For example, it can be applied to any shape such as an elliptical shape, a hexagonal shape, and an octagonal shape.

[0077] FIG. 7 shows another test result of the press-fitting in-house. Here, a high-tensile steel plate (tensile strength 80 kgfZmm ² ) was used as the plate 8. Nut 2 is M10 standard, and the press-fit allowance (d) is 0.3 mm. This test measures the bonding strength against the current value during energization. As the energization pattern, a basic pattern (energized only during press-fitting) and a preheating pattern (performing energization to generate preheating prior to press-fitting energization) were tested. The bonding strength was measured by indentation peel strength (KN) based on JIS standard (B1196).

[0078] As a result of the test, when the current value is 18 KA or more, the intensity exceeds 20 KN and converges to about 30 KN. In addition, the preheat pattern joining form is better than the basic pattern. This is because by providing a preheating process, the resistance heat is evenly distributed throughout the joint during press-fitting, so that a stable and good joining environment is obtained and excellent strength is obtained. Conceivable.

[0079] Here, an in-house test compared the indentation peel strength between the above-mentioned press-fitting and conventional projection welding, and the results are shown. In this test, the above press-fit Indentation peel strength of a steel plate (plate) with different tensile strength (press-fit joint nut) and indentation peel strength of a conventional steel plate welded to a similar steel plate (general weld nut) Were measured and compared for various applied current values during energization.

[0080] SPCC steel plates (tensile strength: 270 MPa (28 kgf / mm ² )), 780 MPa steel plates (tensile strength: 780 MPa (80 kgf / mm ² )) and 980 MPa steel plates (tensile strength: 980 MPa (lOOkgf / mm) ² ) Three types of different bows are used. Of these, the 780 MPa steel plate and the 980 MPa steel plate are so-called high-tensile steel plates.

[0081] In addition, nuts of M6 size (nominal thread size) are used, and in press-fitting, the allowance for press-fitting with the hole in the steel sheet is 0.3 mm, and the pressurizing force during press-fitting is 400 kgf. Joined. On the other hand, in projection welding, four projections were provided on the M6 nut and welded to the plate. For each steel plate, the peel strength with respect to the applied current during welding was measured, and the relationship between the current and the peel strength was examined.

[0082] Fig. 8 (a) shows the applied current when a nut is joined and welded to the SPCC steel plate as a plate.

6 is a graph comparing (kA) and indentation peel strength (kN) for the press-fit joint nut and the general weld nut. With this graphing force, in the case of press-fit joint nuts, the indentation peel strength is stipulated by JIS standards. 3. Current that is considered to be weldable to the welding current limit that is greater than the applied current at which 24kN or more is secured. The range (S) (current range for welding) is approximately 6.5 kA. This welding limit current is the limit of current that will cause overheating due to excessive heating of the joint if a current higher than this is applied, causing problems in press-fit welding. Also, in the case of general weld nuts, the indentation peel strength is above the current at which the above 6JIS standard 3.24kN or more is secured, and the weldable current range (P) up to the current limit due to spatter generation is approximately 3kA. . This spatter generation limit current is the limit of current at which a flow beyond this level causes explosion at the weld and a stable welding performance cannot be obtained.

[0083] Fig. 8 (b) is a comparative graph of the press-fit joint nut and the general weld nut obtained by joining the nut to the 780 MPa steel plate, and Fig. 8 (c) is a graph comparing the nut with the 980 MPa steel plate. It is a comparison duragram about the above-mentioned press-fit joint nut and general weld nut joined and welded to each other. Figure 9 shows the comparison results for the above weldable current range and maximum joint strength. It is a stopped table.

[0084] From the above, the press-fit joint nut has a wider weldable current range (S) (about twice) than the weldable current range (P) of general weld nuts, and has a large degree of freedom in welding conditions! /, . This is because press-fit joining can keep the joining temperature low, and it is thought that no spatter or explosion occurs during joining. Thus, in press-fit joining, the degree of freedom of welding conditions is large, so even if the welding conditions change depending on the size of the joining member, etc., current control can be performed with a constant width, so control is easy and workability is improved. Is good.

[0085] In addition, the indentation peel strength of the press-fit joint nut is higher than that of the steel plate with lower tensile strength (10kN for SPCC steel plate) than that of the above three types of steel plates. The peel strength tends to be higher in the case of 780MPa steel plate and 980MPa steel plate (12kN for both). On the other hand, the indentation peel strength of the above general weld nut is about the same as about 10 kN for any of the above three types of steel plates. From the above graph, the peel strength tends to be higher when bonded to a steel plate with lower tensile strength. . In this way, the indentation peel strength of the press-fit joint nut increases in proportion to the tensile strength of the steel sheet because the strength of the base material is directly reflected in the high peel strength. In addition, the indentation peel strength of general weld nuts does not increase according to the tensile strength of the high-tensile steel sheet because when the nut is welded to the high-strength steel sheet, an oxide film is easily formed on the welded part and the welding temperature is high. It is conceivable that the weld is annealed.

[0086] As described above, from the above in-house test, the press-fit joint nut has a higher degree of freedom in the joining conditions such as the applied current at the time of joining than the general weld nut, so that control of current control and the like are easy and workability is improved. It is possible to obtain high peel strength when the nut is bonded to the steel plate, and excellent press-bonding characteristics in various respects, such as excellent bonding strength especially when bonded to high-strength steel plates. It could be confirmed.

[0087] Further, in-house tests compared the indentation peel strength when a nut was joined and welded to a steel plate as a plate, and the results are shown. In this test, the indentation peel strength of the press-joined nut to the 590 MPaGA steel plate (alloyed hot-dip galvanized steel plate) (press-fit welded nut) and the conventional projection welded nut to the same steel plate. Measure the indentation peel strength of the welded item (general weld nut) for various applied current values! We compared. Other welding conditions are the same as in the case of the in-house test.

FIG. 10 is a graph comparing the applied current (kA) and the indentation peel strength (kN) when the nut is joined and welded to the GA steel sheet, for the press-fit joint nut and the general weld nut. With this graphing force, in the case of press-fit joint nuts, the indentation peel strength is more than the applied current that secures the above 6JIS standard value and the weldable current range (S) up to the welding current limit is about 4.5kA. It is. In the case of general weld nuts, the weldable current range (P) up to the current limit due to spatter generation is approximately 2 kA, which is greater than the current at which the indentation peel strength is secured above the JIS standard value.

[0089] From the above, the press-fit joint nut has a wider weldable current range (S) (more than twice) compared to the weldable current range (P) of a general weld nut, and a large degree of freedom in welding conditions! /, . In particular, in the case of a general weld nut, the current limit (approximately 9 kA) due to spatter generation is lower than that of the steel plate (current limit (approximately 10 kA) of the 780 MPa steel sheet) without the above-mentioned plating. This is because, when the nut is welded to the GA steel plate by general welding, the occurrence of spatter sparks significantly hinders welding. Such a large amount of spatter has an adverse effect on product quality, such as making the screw part of the nut defective, the work is dangerous, and it is a problem in terms of safety. For this reason, when a nut is generally welded to a steel plate, a large amount of spatter is generated and the degree of freedom of welding conditions is reduced, current control is difficult and workability is poor.

[0090] On the other hand, in the case of press-fit joining, almost no spatter is generated. Therefore, welding can be performed well in a wide current range. Therefore, the indentation peel strength of the press-fit joint nut is within the current range (S) that can be welded. A stable high and strength characteristic can be obtained. In this way, according to the above in-house test, even when a plated steel plate is used for the plate, the press-fit joint nut provides a high peel strength in a wide current range, and the peel strength similar to that of the non-plated steel plate is obtained. In addition, compared to general welding nuts, the degree of freedom in joining conditions such as applied current during joining is higher. Therefore, it was confirmed that current control is easy and the workability is good.

[0091] In a structural body such as an automobile, a steel sheet formed on a framework structure or body is used as an element member. As the element member, a plate 8 with the nut 2 fixed thereto is used. As shown in FIG. 11, the plate 8 to which the nut 2 is joined is assembled as an element part constituting a structural body such as an automobile frame, and a bolt 19 is tightened thereto. It can be used for other purposes such as fixing other components 20.

Therefore, according to the press-fit joining according to the above-described embodiment, the press-fit and energization are simple steps.

In addition, it can be joined quickly, can be easily manufactured, has a low manufacturing cost, and is economical. In addition, since the bonding interface is cleaned and bonding is performed well, the strength is excellent, and since the bonding is solid-phase welding, the heat affected area on the base metal is small. There is an effect that accurate joining is ensured and finishing accuracy is good.

[0093] Further, in the press-fit joining, since the joining is performed over the entire circumference, the airtightness of the joining portion can be ensured. Ensuring such airtightness has been structurally difficult with conventional process welding, and a separate seal has been required to ensure confidentiality. In addition, some conventional projection welding nuts have a guide projection at the center, but there is a standard gap between the guide projection and the hole in the plate. In some cases, the center position of the nut may be shifted from the center of the hole. In this case, the seating surface may be deformed when bolted. In this regard, in the above-described press-fit joining, the position accuracy of the nut 2 is good because the structural force that enters the hole can be automatically positioned and the center position coincides with the center of the hole with high accuracy.

[0094] Next, another embodiment will be described. As shown in FIG. 12, the nut 22 used in this embodiment is formed by forming a plurality of ridges 25 on the outer periphery of the protrusion 26. The nut 22 has a shape in which convex strips 25 are formed at four equally spaced positions as a result of flattening out the four outer diameter portions of the protruding portion 6 of the nut 2. Therefore, at the time of press-fitting, these ridges 25 are partially joined to the wall surface of the hole 10 of the plate 8. Therefore, this joining structure is a partial joining in which a plurality of portions of the protruding portion 26 of the nut 22 are joined to the hole 10 of the plate 8.

[0095] The basic joining process of this press-fit joining is the same as that of the above-mentioned all-round joining, but since the area where both the members are in contact with each other is small, the electrical resistance during energization is increased, and the current during energization is increased. The difference is that the same resistance heat can be obtained even if the value is lowered. The applied current during press-fitting in this joining process is 22 kA and the applied pressure is 400 kgf.

[0096] Between the protruding portion 26 of the nut 22 and the hole 10 of the plate 8, the diameter is in the range of 0.2 mm to 1. Omm (preferably 0.3 mm to 0.7 mm). A press-fitting allowance is formed. This As a result, the hole 10 and the protrusion 26 of the plate 8 are brought into contact with the four protruding strips 25 and press-fitted.

When joining, the plate 8 is placed on the upper surface of the lower die 14, while the upper die 16 fitted with the nut 22 fitted in the hole 18 is lowered together with the nut 22. Then, the upper die 16 is pressed with a certain pressure applied, and at the same time, the nut 22 and the plate 8 are energized through the lower die 14 and the upper die 16. Then, press-fitting of the protruding portion 26 is started as the electric resistance heat is generated, and the protruding portion 25 moves down in the hole 10 of the plate 8 so that the tip of the protruding portion 26 is in the middle position of the hole 10 of the plate 8. To reach. In this case, an ironing action is produced at the joint interface between the ridges 25 and the inner walls of the holes 10 of the plate 8, and press-fitting by ironing is performed. By such a manufacturing process, a member having a press-fit joint structure including the nut 22 and the plate 8 is obtained.

[0098] As another form of the partial bonding, the outer diameter of the protruding portion 26 is circular, while the inner peripheral portion of the hole 10 of the plate 8 is cut out in a plurality of portions, and a plurality of connecting portions with the protruding portion 26 are provided. The same effect as that of the partial bonding can be obtained with this configuration as well as the formed configuration.

Therefore, according to the press-fit joining according to the above-described embodiment, the joining can be performed quickly and easily by a simple process of only press-fitting and energization, the production cost is low, and the economy is excellent. In addition, since the joining is performed well and the strength is excellent, and the joining is performed in a solid-phase state, high-precision joining is ensured and finishing accuracy is good.

Next, according to a second embodiment, a nut with a flange as a fastening member for press-fitting and a press-fitting joint structure will be described with reference to the drawings. FIG. 13 shows the nut 32 with the flange. The nut 32 has a base portion 33 having a hexagonal outer shape, a hollow disc-shaped flange portion 41 formed integrally with a lower portion of the base portion 33 and having a larger outer diameter than the base portion, and a screw hole 34 penetrating the center portion of the base portion 33. And a projecting portion 36 that projects downward from the periphery of the hole portion of the flange portion 41 in a cylindrical shape. The projecting portion 36 has a circular cylindrical shape (annular shape) having a predetermined thickness (s), and a hole continuous with the screw hole 34 and the hole portion of the flange portion 41 is formed therein. . The protrusion 36 is formed so as to protrude downward from the back surface 35 of the flange 41 with a predetermined height width (h).

[0101] FIG. 14 shows another form of flanged nut 42 for press-fit joining. As with the nut 32, the nut 42 also protrudes from the rear surface 35 of the flange 41. Further, a groove storage portion 39 is formed on the back surface portion 35 of the flange portion 41 so as to have an annular groove force in a state of surrounding the protrusion portion 36. The nut 42 is formed by pressing the central portion of the upper surface of the base portion 33 with a press carriage (recess 43) and extruding the protruding portion 36 downward.

[0102] Further, the nuts 32 and 42 with the flange have engraved screw grooves all over the base portion 33, the flange portion 41, and the protruding portion 36. However, this is because the screw grooves are engraved only in the base portion 33 and the flange portion 41. The screw groove may not be formed in the hole portion of the projecting portion 36. At this time, the inner diameter of the hole portion of the projecting portion 36 is set to be approximately the same as the inner diameter of the thread valley of the base portion 33 or a slightly larger diameter. Thereby, when the nuts 32 and 42 are fastened with bolts, the condition of the bolts is improved. In addition, it is possible to form a screw groove only in the hole portion of the base portion 33 and not to make a screw groove in the hole portions of the flange portion 31 and the protruding portion 36. Become better

[0103] The burr storage part 39 has various forms as shown in FIG. 15. For example, the burr storage part 39 shown in FIG. This is a form in which a groove is provided along the vicinity. The burr storage part 39 shown in FIG. 5B is a form in which a taper-like groove part is provided on the back face part 35 of the flange part 41 so that the force in the vicinity of the protrusion part 36 is inclined downward toward the outside.

[0104] Regarding the shape of the base portion 33 of the nut with flange, it is possible to adopt a polygonal shape of any shape such as a hexagon or a square, and it is also possible to adopt a circular shape. A flange portion is integrally formed on these base portions, and a protrusion 36 is formed on the back surface portion of the flange portion, whereby a nut for press-fit joining can be obtained. Further, the size of the flange portion 41 is formed larger than the outer diameter (maximum diameter) of the base portion 33 to secure the area of the seat surface. As the shape of the flange portion 41, various shapes such as a circle, an ellipse, and a flower shape can be adopted. Further, the seating surface of the back surface portion 35 of the flange portion 41 here is flat.

FIG. 13 (c) shows the plate 38 to which the nut 32 is press-fitted and joined. The plate 38 is a plate material having a predetermined plate thickness (t), and a circular hole 40 is formed at a predetermined position. The hole 40 is a straight hole that is orthogonal to the plate 38 surface. The plate 38 has a flat portion where the joint with the nut 32 is flat. If there is a slight bend in the side, but the degree is slight, there is no problem in joining.

A chamfered portion 37 is formed on the projecting portion 36 of the nut 32 as shown in FIG. 13 and the like, and the height width of the chamfered portion is about 0.3 mm. The chamfered portion 37 is formed for the convenience of molding, and is also effective as a guide for press-fitting. Note that the chamfered portion 37 is eroded and there is almost no original shape after the press-fitting because there is a predetermined press-fitting allowance during press-fitting. The height width (h) of the projecting portion 36 of the nut 2 is a concept including the chamfered portion 37. The wall thickness (s) of the protruding portion 36 is a dimension between the valley of the screw groove of the screw hole 34 and the outer diameter portion of the protruding portion 36, and when the screw groove is not provided, the protruding portion 36 is provided. This is the wall thickness.

In this embodiment, regarding the relationship between the plate thickness (t) of the plate 38 and the height width (h) of the protruding portion 36 of the nut 32, the height width (h) is the plate thickness ( The dimensions are as small as (t) (h = t, h ku t). This is because when the protrusion 36 is press-fitted in excess of the plate thickness (t) of the plate 38, press-fitting is performed beyond the joining range of both members, and this is a good joint interface formed by press-fitting. This is because the strength of the joint is reduced by crushing and creating a new joint interface. Also, if the height width (h) of the protruding portion 36 of the nut 32 is larger than the plate thickness (t), the protruding portion 36 protrudes from the plate 38 after joining, and this protruding portion is attached when other parts are assembled by tightening the nut. May be inconvenient.

[0108] The plate 38 is made of a high-tensile steel plate that is employed as a structural component such as a member or panel of an automobile. This high-strength steel sheet includes steel sheets containing alloying elements such as C, Si, Ti, Nb, etc., or dual-phase (DP) steel sheets that have been heat-treated, and have a bow I tension strength of S780 NZmm ² or more. Have In resistance welding, the influence of the acid coating is generated when the tensile strength is 780 NZmm ² or more, and the excellent effect of the press-fitting according to this embodiment is exhibited.

[0109] Regarding the material of the nut 32 and the plate 38, in particular, when the steel or high-strength steel nut 32 is connected to the plate 38 having a high-strength steel plate force, there is little influence of the acid coating or the like. Compared with the projection welding nuts of this type, welding defects do not occur, which is preferable. Of course, the plate 38 and nut 32 are made of steel for general processing, high-tensile steel for automobiles, other metal materials, SUS (stainless steel), SUS and carbon steel. , Carbon steel for machine structure, alloy steel for machine structure, heat resistant steel, tool steel, panel steel, pig iron, free-cutting steel, bearing steel, steel for general processing, steel for pressure vessel, titanium, aluminum Light metals such as yuum and magnesium, light metal alloys, and the like are applicable. It can also be applied to surface-treated high-tensile steel sheets such as zinc plating used in automobiles, and can also be applied to surface-treated nuts.

[0110] Here, the press-fit joining for joining the nut 32 with the flange to the plate 38 will be described. As shown in FIG. 16, this press-fit joining uses a jig having a lower die 44 and an upper die 46 made of chrome copper, and joins the protruding portion 36 of the nut 32 to a plate 38 as a base material. A hole 48 for tightly holding the nut 32 is provided at the center of the upper mold 46 of the jig, and the lower mold 44 and the upper mold 46 function as electrodes.

[0111] The hole 48 of the upper mold 46 is in close contact with the upper surface and the side surface of the nut 32 to reduce electric resistance. In addition, the lower end of the hole 48 is positioned slightly above the back surface 35 of the nut 32 to prevent contact between the electrodes. The upper mold 46 can be used in a flat form without the hole 48.

As shown in FIG. 16, a predetermined press-fitting allowance (d) is formed between the protrusion 36 and the hole 40 of the plate 38. This press-fitting allowance (d) is a dimension with respect to the diameter (d = diameter of the projecting portion 36−diameter of the hole portion 40), and is (dZ2) with respect to the radius. In order to secure the press-fitting allowance, the diameter of the hole 40 of the plate 38 is set to be smaller than the diameter of the protruding portion 36 of the nut 32. As the conditions for press-fit joining, when an M8 standard nut was used for the base and a 780 NZmm ² high-tensile steel plate with a thickness of 2.8 mm was used as the plate, the applied current was 16 kA and the pressing force was 2 kN. This applied pressure is set to a pressure lower than the stress of the plate 38 as a base material (here, a resistance force that prevents the protruding portion from entering the hole of the plate). Accordingly, when the applied pressure exceeds the stress reduced by the softness of the plate, the press-fitting is started.

[0113] In an example of this press-fitting process, the plate 38 is placed on the upper surface of the lower die 44, the nut 32 is held in the hole 48 of the upper die 46, and the nut 32 is lowered together with the upper die 46. . Then, alignment is performed in a state where the lower end portion of the protruding portion 36 is in contact with the edge of the hole portion 40. Next, the upper mold 46 is pressed with a certain pressure applied, and then (after about 1 second), the lower mold 44 and the upper mold 46 are pressed. A joining current is passed between the nut 32 and the plate 38 via 46.

Then, press-fitting of the protruding portion 36 into the hole 40 is started as the electric resistance heat is generated, and the protruding portion 36 moves vertically down in the hole 40 of the plate 38. Then, the leading end portion of the projecting portion 36 reaches the intermediate position of the hole portion 40, and at the same time, the back surface portion 35 (seat surface) of the nut 32 is in close contact with the surface of the plate 38. By such a manufacturing process, a press-fit joined part composed of the nut 32 and the plate 38 is obtained. This joining structure is an all-around joining in which the entire circumference of the protruding portion 36 of the nut 32 is joined to the hole 40 of the plate 38. In addition, the timing in each said process and the transition timing between processes are controlled by time.

[0115] When a high-tensile steel material having a carbon equivalent of 0.35 or more is used for the nut 32 and the plate 38, when the press-fit joining method according to this embodiment is used, due to the rapid cooling effect after the press-fit joint, A martensitic structure may occur in the heat affected zone. This metal structure is very hard and brittle, which causes problems in the toughness of the joint. As a means to prevent this, it is effective to flow a secondary current using the same joining jig following the press-fitting and joining process, heat the joint to heat and anneal this part. By this tempering energization, the martensite is changed to tempered martensite, and the toughness is recovered at the joint.

[0116] Further, prior to the press-fitting step, it is possible to employ a (preheating pattern) joining method that incorporates a preheating step in which the nut 32 and the plate 38 are preheated. The purpose of this preheating is to prevent quenching of the joint after joining and to suppress the generation of martensite. In this preheating process, before starting the press-fitting, the energizing current is kept lower than that at the time of the press-fitting (preheating current of about 1Z2 at the time of press-fitting), and energization is performed with both members in contact with each other. In this preheating step, the upper mold 46 is lowered in the same manner as in the press-fitting step, and a preheating current is applied in a state where the lower end portion of the protrusion 36 is in contact with the edge of the hole 40. Here, since the purpose is to preheat the nut 32 and the plate 38 as the members to be joined, the temperature of both the members is raised so that the joint portion between the two members does not soften. Immediately after this preheating step, the energization current is increased and the above press-fitting step is started.

[0117] In the above press-fitting process, the press-fitting of the nut 32 is started as the electric resistance heat is generated, and the projecting portion 36 moves down in the hole 40 of the plate 38. In this case, ironing action occurs at the joint interface between the two members, and press-fitting is performed by a manufacturing process using ironing. And one Press-fit joining is performed at a constant applied pressure and a constant descent rate, and the joint is heated instantaneously, so that the nut 32 is press-fitted and joined in a short time, and the back surface 35 of the nut 32 abuts against the surface of the plate 38. To complete the joining. Then, the protruding portion 36 of the nut 32 and the hole portion 40 of the plate are joined together with a solid-phase joining interface formed therebetween. Solid-phase welding provides a clean surface structure on the joint surface, which results in good joining and high joint strength.

[0118] In solid phase welding, whether or not a clean structure can be obtained at the joint interface affects the quality of the joint. According to the press-fit joining according to this embodiment, the wall surfaces of the protruding portion of the nut 32 and the hole portion 40 of the plate 38 are slid by the sliding movement at the joining interface, thereby The impurity layer is removed, the surface is cleaned, and the joint becomes clean and woven.

[0119] Thereafter, as the press-fitting progresses, the joint area of the joint surface portion increases, and conversely, the cross-sectional area difference decreases, so that the electrical resistance decreases, and as a result, the generation of resistance heat decreases and the temperature of the joint surface portion decreases. . The joining state by the press-fitting is a solid state joining accompanied by plastic deformation (thermoplasticity) by press-fitting. Then, after the press-fitting is completed, the hardness of the base material of the joint is recovered by cooling, and the joint is firmly joined. As a result, the nut 32 and the hole 40 of the plate 38 are metal-to-metal bonded, so that a perfect seal is obtained. Here, in the press-fit joining, the process of pressurization → energization → press-fit → cooling is followed. Also, the burrs generated by the shaving are housed in the barrier housing part 39, whereby the back surface part 35 of the nut 32 is brought into close contact with the surface of the plate 38, and the sealing performance and quality are good. Is obtained.

[0120] In this way, the seating surface of the nut uniformly adheres to the plate, so that it is possible to demonstrate the high load characteristics and secure a wide seating surface that are characteristic of nuts with flanges, such as shaking, bending, twisting, etc. The original purpose of the nut with a flange, which is to reinforce, is achieved. Especially when the plate 38 is thin (about 1. Omm), the plate 38 is effectively reinforced by the seating surface of the flange 41. The In addition, since the nut flange 41 is not fixed to the plate 38, it is possible to prevent the surface from biting by a minute lateral movement applied to the joint, which is particularly effective when the plate 8 is thin. .

[0121] Here, the force which is a problem such as the strength of the flanged nut is explained in the first embodiment. The nuts used in the in-house test A and the in-house test B were the same as those used for the nuts without a flange and provided with a protruding part.These tests were conducted at the height of the protruding part of the nut. Width (h) and wall thickness (s) This is a test for shrinkage and strength of the inner diameter, both of which have nothing to do with the presence or absence of the flange, so even for nuts with flanges The result is similar.

[0122] Therefore, for a nut with a flange, the protruding height width (h) of the protruding portion of the nut is 0.5 mn! 2. Within the range of Omm, the degree of contraction of the inner diameter of the protrusion 36 is considered to be generally good. The wall thickness (s) of the nut protrusion 36 is 1. Omn! In the range of ~ 2.5mm, sufficient and strong strength is ensured. From this, the thickness (s) of the nut protruding portion 36 is 1. It is considered that the contraction degree of the inner diameter of the protruding portion 36 is generally good within the range of Omm or more. Further, the thickness (s) of the nut protrusion 36 is sufficiently strong within the range of 1.0 mm to 2.5 mm. In addition, when the press-fitting allowance d is about 0.1 mm, the amount of shaving at the press-fitting allowance during press-fitting is small and the joining is unstable. In addition, when the press-fitting allowance d is 0.6 mm or more, the amount of shaving due to the press-fitting allowance increases, resulting in uneven finish.

In this embodiment, for ease of processing, the force that makes the outer shape of the protruding portion 36 of the nut 32 and the shape of the hole portion 40 of the plate 38 circular is the same even if these are other shapes. If there is a similar relationship, the press-fitting conditions are satisfied, and the present invention can be applied to shapes such as an elliptical shape, a hexagonal shape, and an octagonal shape.

[0124] Also, the results confirmed by the above in-house test (comparison of indentation peel strength between press-fit joints and conventional process welds) are the same for nuts with flanges. Therefore, the degree of freedom in joining conditions such as applied current during joining is high, so current control is easy to control and workability is good.In addition, excellent joining strength can be obtained especially when joining with high tensile strength steel sheets. In addition, even when a plated steel plate is used for the plate, the press-fit joint nut is wide, high in the current range, and high peel strength can be obtained.

[0125] Steel structures (thickness of 1.2mn! ~ 2.3mm are often used) are used for structures such as automobiles! Things are used as element members. As this element member, a plate 38 with the nut 32 fixed thereto is used. As shown in FIG. 17, the plate 38 to which the nut 32 is joined is the It is assembled as an element part that constitutes a structural body such as a frame or a frame, and is used for other purposes such as fixing another component part 20 by tightening a bolt 19. At this time, since the seating surface of the nut 32 is in close contact with the plate 38, the accuracy of the mounting position and the perpendicularity of the screw is ensured, the bolt 19 can be screwed in smoothly, and the screw bite at the time of fastening is secured. It is prevented and can be concluded well.

[0126] Therefore, according to the above-described embodiment, the manufacturing process can be performed quickly and easily with only a simple process of press-fitting and energization, and it is economical, and the bonding is performed well and the strength is excellent. In addition, since the joining is solid phase welding, there is an effect that high-precision joining is ensured and finishing precision is good. In addition, since the seating surface of the nut is in close contact with the plate, it is possible to demonstrate the high load characteristics and secure a wide seating surface, which is characteristic of flanged nuts, and to reinforce against shaking, bending, twisting, etc. The original purpose is surely achieved, and the screws can be prevented from loosening during long-term use. In addition, since the members are integrated with each other over the entire circumference at the center of the joint by this press-fit joint structure, the stress is dispersed and a stable strength is maintained. In addition, since the nut flange is not fixed, it is possible to prevent the biting of the surface due to minute lateral movement applied to the joint.

[0127] Further, even when high-tensile steel is used for the plate and nut, strong bonding can be performed and the same strength as that of a mild steel plate can be obtained. This prevents high-strength materials from being used with peace of mind, as troubles caused by hydrogen in steel such as delayed fracture, stress fracture, and hydrogen embrittlement are also released. In addition, in this press-fit joining, it is possible to ensure good quality without worrying about spatters that do not generate spatter as in projection welding, screw defects due to oxides, reduced strength, and poor welding.

[0128] In addition, in the above press-fit joining, since it is completely joined over the entire circumference, it is possible to ensure the sealing performance and airtightness of the joint, and there is no deterioration in sealing performance due to vibration or peeling due to long-term use. . Also, with this press-fit joining, the position accuracy of the nut is good because it can be positioned automatically by the structural force that pushes the nut into the hole, and the center position matches the center of the hole with high accuracy. . Furthermore, even when zinc-plated steel plates are used as plates, this press-fit joining method purifies the joints with a small amount of squeezing action, so that the joint strength variation is small. Good joint strength is obtained, In addition, the electrode is not in contact with the molten zinc, but is in contact with the low temperature zinc, so that the electrode is less likely to be worn.

[0129] Fig. 18 shows a nut 62 with a flange having a flange portion of another shape.

The nut 62 is formed with a protruding portion 36 in the same manner as the nut 32, and the thickness of the end portion of the flange portion 61 is set to about 1. Omm, and the thickness of the boundary portion between the bracket portion 61 and the base portion 33 is set. Is about 1.5mm. Further, the back surface portion 65 of the flange portion 61 is formed in a concave spherical surface as a whole. In this case, the height difference between the vicinity of the central portion of the concave spherical surface of the back surface 65 and the outer edge portion is 0.5 mm or less to prevent a short circuit between the flange portion 61 and the plate 38 in the initial press-fitting. In the second half of the press-fitting, even if the short circuit occurs, the press-fitting part is sufficiently heated, so that there is little effect on the press-fitting joint itself. Then, the entire protruding portion 36 of the nut 62 is press-fitted into the hole 40 of the plate 38. In this way, by reducing the thickness of the flange portion 61, the heat generated during welding allows the flange surface to conform to the shape of the plate 38, and even if the plate 38 is slightly bent, the pressure is relatively uniform. Can be added. In addition, by forming the seating surface of the flange portion 61 in a concave spherical shape, even if the surface of the plate 38 is somewhat uneven, pressure is applied to the entire flange portion relatively uniformly, and the pressure applied to the outer peripheral portion is also increased. Pressure is increased and loosening is prevented.

[0130] Next, a nut with a flange according to another embodiment will be described. As shown in FIG. 19, the flanged nut 52 used in this embodiment has a plurality of ridges 55 formed on the outer periphery as the protrusion 56, and the other shapes are the same as the nut 32 described above. is there. The nut 52 is formed in such a manner that up and down ridges 55 are formed at four equally spaced positions as a result of flattening the four outer diameter portions of the protrusion 36 of the nut 32. is there. Therefore, at the time of press-fitting, the protrusion 55 is partially joined to the wall surface of the hole 40 of the plate 38. For this reason, this joining structure is a partial joining in which a plurality of portions of the protruding portion 56 of the nut 52 are joined to the hole 40 of the plate 38. The material of the flanged nut and plate for press-fit joining according to this embodiment is the same as that of the above embodiment.

[0131] The basic joining process of the press-fitting is the same as that of the press-fitting of the above embodiment. Here, the area where both the members are in contact with each other is small, so that the electric resistance during energization increases and The difference is that the necessary resistance heat can be obtained even if the current value is reduced. Above nut 5 Press-fitting allowance in the range of 0.2mm force against the diameter 1. Omm (preferably 0.3mm to 0.7mm). Is formed.

When joining, the plate 38 is placed on the upper surface of the lower die 44, while the upper die 46 fitted with the nut 52 fitted in the hole 48 is lowered together with the nut 52. Then, the upper die 46 is pressed with a certain pressure applied, and further, the current is passed between the nut 52 and the plate 38 via the lower die 44 and the upper die 46. Then, as the electric resistance heat is generated, press-fitting of the protrusion 56 is started, and the protrusion 55 moves down in the hole 40 of the plate 38, and the tip of the protrusion 56 is in the hole 40 of the plate 38. It reaches an intermediate position. In this case, an ironing action occurs at the joining interface between the ridge 55 and the inner wall of the hole 40 of the plate 38, and press-fitting by ironing is performed. By such a manufacturing process, a member having a press-fit joint structure including the nut 52 and the plate 38 is obtained.

[0133] As another form of the partial joining, the outer diameter of the protruding portion 56 of the nut 52 is circular, while the inner peripheral portion of the hole 40 of the plate 38 is notched in a plurality of portions, and joined to the protruding portion 56. Even in this configuration in which a plurality of locations are formed, the same effect as the partial bonding can be obtained. In the press-fitting according to this embodiment, if the projecting portion of the nut and the hole portion of the plate are in a similar shape relationship with each other, they can be press-fitted together.

[0134] Therefore, according to the above-described embodiment, the manufacturing process can be performed quickly and easily with only a simple process of press-fitting and energization, and the cost is excellent, and the bonding is performed well and the strength is excellent. In addition, since the joining is solid phase welding, there is an effect that high-precision joining is ensured and finishing precision is good. In addition, since the seating surface of the nut is in close contact with the plate, it is possible to demonstrate the high load characteristics and secure a wide seating surface unique to flanged nuts, preventing shaking, bending, and twisting. Also, since the flange part of the nut is not fixed, it is possible to prevent the joint surface from getting caught. Furthermore, even when a high-strength steel plate is used as the base material, strong bonding can be achieved and the same strength as a mild steel plate can be obtained, and even when a galvanized steel plate is used, it is good. High bonding strength can be obtained.

Next, according to the third embodiment, a bolt as a fastening member for press-fitting and a press-fitting structure will be described with reference to the drawings. Figure 20 (a) shows the bolt 72 above. It is. The bolt 72 has a hexagonal head portion 73 and a shaft portion 81. The shaft portion 81 has a circular cross-sectionally enlarged diameter portion 76 at a predetermined height width (h) at a lower position of the head portion 73. A shaft portion 74 is formed which is formed and continuously provided with a screw groove. The diameter (D) of the enlarged diameter portion 76 is formed larger than the diameter (E) of the shaft portion 74.

FIG. 20 (b) shows a panel 78 to which the bolt 72 is press-fitted and joined. The panel 78 is a plate material having a predetermined plate thickness (t), and a circular hole 80 is formed at a predetermined position. The hole 80 is a straight hole that is orthogonal to the panel 78 surface.

Here, the difference (D−E) between the diameter (D) of the enlarged diameter portion 76 of the bolt 72 and the diameter (E) of the screw thread portion of the shaft portion 74 is assumed to be greater than 1 mm. . According to in-house tests, the press-fitting allowance (the difference between the diameter of the enlarged diameter portion 76 and the diameter of the hole 80) in press-fitting is preferably 0.2 mm to 0.6 mm. For this reason, the difference (D−E) is larger than the press-fitting allowance, and is determined to be lmm or more as described above, taking the accuracy of the jig into consideration.

[0138] Further, the height width (h) of the diameter-expanded portion 76 was set in a range of about 1 mm to 5 mm. According to in-house tests, good results were obtained in both strength and finish quality when the height width (indentation depth) in press-fitting was in the range of lmm to 5mm. If this height width (h) is 1 mm or less, the cleaning of the impurity layer on the surface due to ironing during the press-fitting will be insufficient, and a high bonding strength will not be obtained. The amount of burrs scraped by the ironing will increase and the quality will be inferior.

[0139] In solid phase welding, whether or not a clean structure can be obtained at the joint interface affects the quality of the joint. According to the press-fit joining according to this embodiment, the wall surfaces of the enlarged diameter portion 76 of the bolt 72 and the hole portion 80 of the panel 78 are squeezed in the sliding direction at the joining interface. The surface impurity layer is eliminated, the surface is cleaned, and the joint becomes a clean structure.

[0140] In this embodiment, regarding the relationship between the plate thickness (t) of the panel 78 and the height width (h) of the enlarged diameter portion 76 of the bolt 72, the height width (h) is the plate thickness. The dimension is set to a force (h = t, h ku t) that is almost the same as (t). This is because when the enlarged diameter portion 76 is press-fitted more than the plate thickness (t) of the panel 78, the press-fitting is performed more than the joint portion of both parts, and this is formed by the above-mentioned press-fitting. Crushing a good joint interface and creating a new joint interface This is because the combined strength is lowered. Also, if the height width (h) of the enlarged diameter portion 76 of the bolt 72 is larger than the plate thickness (t), the enlarged diameter portion 76 protrudes from the panel 78 after joining, and when other parts are assembled by nut tightening This is because this protruding part may be inconvenient.

[0141] FIGS. 21 (a) and 21 (b) show another form of a bolt 82 for press-fit joining. A head portion 83 of the bolt 82 is circular, and an enlarged diameter portion 76 and a shaft portion 74 are formed as a shaft portion from the back surface portion 75 of the head portion 83. Further, this bolt 82 is formed with a burr storage portion 79 which also has an annular groove force in a state of surrounding the enlarged diameter portion 76 on the back surface portion 75 of the head portion 83. The material of the bolts 72, 82, etc. is steel or steel is high strength steel.

[0142] The burr storage portion 79 has various forms as shown in FIG. 22. For example, the burr storage portion 79 shown in FIG. 22 (a) has a groove along the vicinity of the enlarged diameter portion 76. It is a form. The burr storage portion 79 shown in FIG. 2B is formed by forming a tapered groove portion that deepens the vicinity of the enlarged diameter portion 76 and becomes shallower toward the outside. In this form, a concave space is formed on the entire surface of the portion.

[0143] Regarding the shape of the bolt 72, bolts of any form such as a hexagonal, square, or circular head and a shaft 81 that is short or long can be used. A screw groove is formed on the entire shaft 81. It is also possible to use a bolt provided with a part of the shaft part without a thread groove, and having a pillar shape and a part of the thread groove. By forming an enlarged diameter portion between the head portion of the bolt and the shaft portion, a bolt for press-fitting can be obtained. Polygonal bolts are easy to fix when bolts are threaded.

[0144] Further, in the case of a square bolt (square, hexagon, etc.), the outer diameter of the enlarged diameter portion 76 is formed to be equal to or less than the width dimension of the two parallel surfaces of the bolt. Also, the outer diameter of the enlarged diameter portion 76 is made smaller than the radial size of the head portion. If the size of the head is in this range, the electrodes can be well placed during energization and press-fitting, and the electrical resistance can be reduced. General projection welding bolts have a welding projection on the head bearing surface (back side), so it is necessary to make the head wider, which increases the head shape of the bolt. . However, in the bolt according to this embodiment, in principle, the head of the bolt can be made as small as the size of the enlarged diameter portion 76 (cross section perpendicular to the axis), and the size and weight of the bolt can be reduced. Contributes to quantification.

[0145] The panel 78 uses a high-strength steel plate used as a structural component such as a member of an automobile. This high-strength steel sheet includes steel sheets containing alloy elements such as C, Si, Ti, and Nb, or dual phase (DP) steel sheets that have been heat-treated, and have a bow I tension strength of 780N Zmm ² or more. Have In resistance welding, the effect of the oxide film occurs when the tensile strength is 780 NZmm ² or more, and the excellent effect of the press-fitting according to this embodiment is exhibited.

[0146] The hole 80 formed in the panel 78 is a straight hole orthogonal to the surface of the panel 78. The joint portion of the panel 78 with the bolt 72 is flat. Even if there is some bending in the vicinity of the hole 80 of the nonel 78, there is no problem in joining if the degree is slight.

[0147] Further, a chamfered portion 77 is formed between the shaft portion 74 and the diameter-expanded portion 76 of the bolt 72, and the height width of the chamfered portion is about 0.3 mm. The chamfered portion 77 is formed for the convenience of mold forming, and is also effective as a guide for press-fitting into the hole 80 of the panel 78. Note that the chamfered portion 77 is eroded and has almost no original shape after the press-fitting because there is a predetermined press-fitting allowance at the time of press-fitting. The height width (h) of the enlarged diameter portion 76 of the bolt 72 is a concept including the chamfered portion 77.

[0148] Regarding the material of the bolt 72 and the panel 78, particularly when the steel 72 or the high-strength steel bolt 72 is connected to the panel 78 made of a high-strength steel plate, the influence of the acid coating is small. Compared with general projection welding bolt welding, it is preferable because no welding failure occurs. Of course, as materials for panel 78 and bolt 72, steel plates for general processing, wire rods, high-tensile steel plates for automobiles, other metal materials, SUS (stainless steel), a combination of SUS and carbon steel, carbon for machine structures Steel, alloy steel for machine structure, heat-resistant steel, tool steel, panel steel, pig iron, free-cutting steel, bearing steel, steel for general processing, steel for pressure vessels, light metals such as titanium, aluminum and magnesium, light metal alloys, etc. Is applicable. It can also be applied to high-tensile steel sheets with surface treatment such as zinc plating used in automobiles, and can also be applied to surface-treated bolts.

[0149] Here, press-fit joining for joining the bolt 72 to the panel 78 will be described. This 23, as shown in FIG. 23, a jig having a lower die 84 and an upper die 86 made of chrome copper is used to join the enlarged diameter portion 76 of the bolt 72 to a panel 78 as a base material. A hole 88 for tightly holding the bolt 72 is provided at the center of the upper mold 86 of the jig, and the lower mold 84 and the upper mold 86 function as electrodes.

[0150] The hole 88 of the upper mold 86 is in close contact with the upper surface and side surfaces of the bolt 72 to reduce electric resistance. A hole 87 into which the shaft 74 of the bolt 72 enters is also provided at the center of the lower mold 84. Further, the lower end of the hole 88 of the upper mold 86 is positioned slightly above the back surface 75 of the bolt 72 to prevent contact between the electrodes. The upper mold 86 can be used in a flat form such as the hole 88.

As shown in FIG. 23, a predetermined press-fitting allowance (d) is formed between the enlarged diameter portion 76 and the hole portion 80 of the panel 78. This press-fitting allowance (d) is a dimension with respect to the diameter (d = diameter of the diameter-perforated portion 80 of the expanded diameter portion 76), and is (dZ2) with respect to the radius. In order to secure the above press-fitting allowance, the diameter of the hole portion 80 of the panel 78 is made larger than the diameter of the shaft portion 74 of the bolt 72 so as to be able to pass through, and the size is smaller than the diameter of the enlarged diameter portion 76 of the bolt 72. To do. As a condition of press-bonding, bolt M 8 standard, in the case of high-tensile steel plate 780NZmm ² having a thickness of 2. 8 mm, the applied current was set to 16 kA, applied pressure was 2 kN. This applied pressure is set to a pressure lower than the stress of the panel 78 as a base material (here, the resistance force that prevents the enlarged diameter portion from entering the hole of the panel). Therefore, press-fitting starts from the point in time when the stress reduced by the softness of the pressure force panel is exceeded.

[0152] In an example of this press-fitting process, the panel 78 is placed on the upper surface of the lower die 84, the bolt 72 is held in the hole 88 of the upper die 86, and the bolt 72 is lowered together with the upper die 86. . Then, the shaft portion 74 of the bolt 72 is inserted into the hole portion 80 of the panel 78 and lowered, and alignment is performed with the lower end portion of the enlarged diameter portion 76 in contact with the edge of the hole portion 80. Next, the upper die 86 is pressed with a certain pressure applied, and then (about 1 second later), a joining current is passed between the bolt 72 and the panel 78 via the lower die 84 and the upper die 86. .

Then, the press-fitting of the enlarged diameter portion 76 into the hole 80 is started as the electric resistance heat is generated, and the enlarged diameter portion 76 moves down vertically in the hole 80 of the panel 78. Then, the tip end portion of the enlarged diameter portion 76 reaches the intermediate position of the hole portion 80, and at the same time, the back surface portion 75 (seat surface) of the head portion 73 of the bolt 72 Adheres to the surface of the panel 78. By such a manufacturing process, a part having a press-fit joint structure including a bolt 72 and a panel 78 is obtained. This joining structure is an all-around joining in which the entire circumference of the enlarged diameter portion 76 of the bolt 72 is joined to the hole 80 of the panel 78. Note that the timing in each of the above steps and the transition timing between the steps are controlled by time.

[0154] When high-strength steel materials having a carbon equivalent of 0.35 or more are used for the bolt 72 and the panel 78, when the press-fitting method according to this embodiment is used, due to the rapid cooling effect after press-fitting, A martensitic structure may occur in the heat affected zone. Since this metal structure is very hard and brittle, a problem arises in the toughness of the joint. As a means to prevent this, it is effective to flow a secondary current using the same joining jig following the press-fitting joint process, overheat the joint, and anneal this part. By this tempering energization, the martensite changes to tempered martensite, and the toughness is recovered at the joint.

[0155] Further, prior to the press-fitting step, it is possible to employ a (preheating pattern) joining method in which a preheating step for preliminarily heating the bolt 72 and the panel 78 is incorporated. The purpose of this preheating is to prevent rapid cooling of the joint after joining and to suppress the occurrence of martensite. In this preheating process, before starting the press-fitting, the energizing current is kept lower than that at the time of the press-fitting (preheating current of about 1Z2 at the time of press-fitting), and energization is performed with both members in contact with each other. In this preheating step, the upper die 86 is lowered in the same manner as in the press-fitting step, and a preheating current is applied in a state where the lower end portion of the enlarged diameter portion 76 is in contact with the edge of the hole portion 80. Here, the purpose is to preheat the bolts 72 and the panels 78 as the members to be joined, so the temperature of both members is raised so that the joints between the two members do not soften. Immediately after this preheating step, the energization current is increased and the above press-fitting step is started.

In the above press-fitting process, the press-fitting of the bolt 72 is started as the electric resistance heat is generated, and the diameter-expanded portion 76 moves down in the hole 80 of the panel 78. In this case, a squeezing action is generated at the joint interface between the two members, and press-fit joining is performed by a manufacturing process by ironing. Then, press-fitting is performed at a constant applied pressure and a constant descent rate, the joint is heated instantaneously and the bolt 72 is press-fitted in a short time, and the back surface 75 of the bolt 72 is connected to the front surface of the panel 78. To complete the joining. The enlarged diameter portion 76 of the bolt 72 and the hole portion 80 of the panel are joined together with a solid-phase welding joint interface formed therebetween. According to solid phase welding, A clean surface structure is obtained, which results in good bonding and high bonding strength

[0157] Thereafter, as press-fitting proceeds, the joint area of the joint surface increases, and conversely, the cross-sectional area difference decreases, resulting in a decrease in electrical resistance, resulting in a decrease in the generation of resistance heat and a decrease in the temperature of the joint surface. . The joint state by the press-fit joint is the one resulting in the solid phase welding accompanied by the plastic deformation (thermoplasticity) by the press-fit. Then, after the press-fitting is completed, the hardness of the base material of the joint is recovered by cooling, and the joint is firmly joined. As a result, the bolt 72 and the hole 80 of the panel 78 are metal-to-metal bonded, so that a perfect seal is obtained. Here, in the above press-fit joining, the process of pressurization → energization → press-fit → cooling is followed. Also, the burrs generated by the shaving are stored in the burr storing portion 79, whereby the back surface portion 75 of the bolt 72 is brought into close contact with the surface of the panel 78, the sealing performance and the quality are good, and the parts of the joining structure are formed. can get.

[0158] Here, the in-house test of the press-fitting and the results will be described. In this test, a high strength steel plate (tensile strength 780 NZmm ² ) with a thickness (t) of 2.8 mm was used as the panel 78. The press-fitting allowance (d) was 0.3 mm with respect to the diameter. Bolts 72 were of the size of M8 standard, the outer diameter of this enlarged diameter part 76 was about 11 mm, and the protruding height width (h) of the enlarged diameter part 76 was 2.5 mm. The bonding strength was measured by indentation peel strength (kN) based on JIS standard (B1196). The test result showed that the peel strength was 10.2 kN and good strength was obtained. Incidentally, the indentation peel strength (kN) of the M8 bolt in JIS standard (B1196) is 6.24kN.

[0159] In the in-house test, the press-fitting allowance (d) is set to 0.3 mm, but the press-fitting allowance (d) is 0.2 mm to 0.6 mm (preferably 0.3 mm to 0.5 mm). In-house tests have confirmed that good results can be obtained within this range. If the press-fitting allowance d is about 0.1 mm, the amount of press-fitting allowance during press-fitting is small and the joining is unstable, and if the press-fitting allowance d is 0.6 mm or more, the amount of cut by the press-fitting allowance is not enough. Increased and uneven finish.

[0160] Steel structures (thickness of 1.2mn! ~ 2.3mm are often used) are used for structures such as automobiles! Things are used as element members. As this element member, a panel 78 to which the bolt 72 is fixed is used. As shown in FIG. 24, the panel 78 to which the bolts 72 are joined is an automobile member. It is assembled as a component part that constitutes a structure such as a frame, and is used for applications such as fixing other component parts 90 by tightening nuts 89 to this.

[0161] Therefore, according to the press-fitting according to the above-described embodiment, it is possible to perform a quick joining with a simple process of only press-fitting and energization, easy to manufacture, and excellent in economic efficiency. In addition, since the bonding interface is cleaned and bonding is performed well, the strength is also excellent. In addition, since the bonding is solid-phase welding, the heat affected area on the base metal is small and highly accurate bonding is achieved. Is ensured, and high-quality products with good finishing accuracy can be obtained. In this press-fit joint, the seating surface of the bolt head is in close contact with the panel surface, so there is no deformation or sag of this part, and it is possible to prevent loosening of the screw. In addition, in this press-fit joining, it is possible to secure a good quality without worrying about spatters that do not generate spatter as in projection welding, screw defects due to oxides, reduced strength, and poor welding.

[0162] In addition, since the above press-fit joining is completely joined over the entire circumference, the sealing property and air tightness of the joint part can be secured, and the sealing property is not deteriorated due to vibration or peeling due to long-term use. ,. Ensuring such airtightness has been structurally difficult with conventional projection welding, and it has been necessary to perform a separate seal to ensure airtightness. In addition, this press-fit joining is favorable because the positioning accuracy of the bolt can be automatically determined by the structural force that pushes the bolt into the hole, and the center position coincides with the center of the hole with high accuracy.

[0163] Furthermore, even when a high-strength steel material is used as the base material, strong bonding can be performed and the same strength as that of a mild steel plate can be obtained. Further, since the press-fit joining is solid-phase joining, hydrogen does not enter the joint unlike arc welding or the like in which the joint melts. For this reason, in this press-fit joining, hydrogen does not enter the high-strength steel panel or high-strength steel bolt, and the troubles caused by hydrogen in the steel such as slow failure, stress fracture, and hydrogen embrittlement are released, You can use these high-strength materials with peace of mind.

[0164] Even when galvanized steel sheets are used, this press-fit joining method uses a small amount of squeezing action to purify the joints, so that the joint strength is small and good. Bonding strength is obtained, and since the electrode contacts low-temperature zinc rather than contacting molten zinc, the electrode is less likely to wear. Also, if the panel thickness is relatively thick, it is automatically corrected by press-fitting bolts into the holes in the orthogonal direction. Is performed to improve the right angle accuracy between the bolt and the panel, and the positional accuracy is also good.

[0165] The cross sections of the enlarged diameter portion 76 of the bolt 72 and the hole portion 80 of the panel 78 are both circular for ease of processing, but this may be other shapes such as an ellipse or a hexagon. By making the two members have similar shapes, the press-fit joining can be performed, and the same effect as described above can be obtained.

[0166] Next, press-fitting bolts according to other embodiments will be described. As shown in FIG. 25, the bolt 92 used in this embodiment has a plurality of ridges 95 formed on the outer periphery as an enlarged diameter portion 96. The bolt 92 has a configuration in which up and down ridges 95 are formed at four equally spaced positions as a result of flattening the four outer diameter portions of the enlarged diameter portion 76 of the bolt 72. It is. Therefore, when press-fitting, the protruding portion 95 is partially joined to the wall surface of the hole 80 of the panel 78. For this reason, this joint structure is a partial joint in which a plurality of portions of the enlarged diameter portion 96 of the bolt 92 are joined to the hole 80 of the panel 78. The material for bolts and panels for press-fitting according to this embodiment is the same as that of the above-mentioned embodiment.

[0167] The basic joining process of this press-fit joining is the same as that of the above-mentioned all-round joining, but since the area where both the members are in contact with each other is small, the electrical resistance during energization increases, and the current during energization increases. The difference is that the required resistance heat can be obtained even if the value is lowered. The press-fitting allowance in the range of 0.2 mm to 1. Omm (preferably 0.3 mm to 0.7 mm) with respect to the diameter between the enlarged diameter portion 96 of the bolt 92 and the hole portion 80 of the panel 78. Is formed!

In joining, the panel 78 is placed on the upper surface of the lower die 84, while the upper die 86 fitted with the bolt 92 fitted in the hole 88 is lowered together with the bolt 92. Then, the upper die 86 is pressed with a certain applied pressure, and further energized between the bolt 92 and the panel 78 via the lower die 84 and the upper die 86. Then, as the electric resistance heat is generated, press-fitting of the enlarged diameter portion 96 is started, and the ridge 95 is moved down in the hole 80 of the panel 78, and the distal end portion of the enlarged diameter portion 96 is in the hole 80 of the panel 78. It reaches an intermediate position. In this case, ironing action occurs at the joint interface between the ridge 95 and the inner wall of the hole 80 of the panel 78, and press-fitting is performed by ironing. By such a manufacturing process, a member having a press-fit joint structure including the bolt 92 and the panel 78 is obtained.

[0169] As another form of the partial joining, while the outer diameter of the enlarged diameter portion 96 of the bolt 92 is circular, The same effect as that of the partial bonding can be obtained with this configuration in which a plurality of inner peripheral portions of the hole 80 of the panel 78 are notched and a plurality of joint portions with the enlarged diameter portion 96 are formed. In the press-fitting according to this embodiment, if the portion where the diameter-expanded portion of the bolt and the hole portion of the panel are in contact with each other has a similar shape, they can be press-fitted together.

[0170] Therefore, according to the press-fitting according to the above-described embodiment, the manufacturing process can be performed quickly and easily with only a simple process of press-fitting and energization, and the cost efficiency is excellent. In addition, since the joining is performed well and the strength is excellent, and the joining is performed in a solid phase state, high-precision joining is ensured and finishing precision is good. In addition, even when a high-strength steel plate is used as the base material, strong bonding can be achieved and the same strength as a mild steel plate can be obtained, and hydrogen in steel such as delayed fracture, stress fracture, and hydrogen embrittlement can be obtained. The trouble power caused by this is relieved and these high-tensile materials can be used with confidence. Even when galvanized steel sheets are used, good bonding strength can be obtained.

Explanation of symbols

[0171] 2, 12, 22, 32, 42, 52 Nut

3, 33 base

4, 34 screw holes

5, 35, 75 Back side

6, 26, 36, 56 Projection

8, 38 plate

10, 40, 80 hole

32, 42, 52, 62 Nut with flange

39, 79 Bali storage

41 Flange

72, 82

73, 83

76, 96 Expanded part (protruding part)

78 Panel (plate material)

Claims

The scope of the claims

[1] Base force Along with the screw part, the base part protrudes to a larger diameter than the screw part, and is solid-phase joined to the hole provided in the plate by press-fitting with electrical resistance heat to form a cross-section with a shape similar to that of the parenthesis hole. A fastening member for press-fit joining, characterized by having a protruding portion provided with a predetermined press-fit allowance.

[2] A joining structure of a plate member provided with a hole at a predetermined position and the fastening member according to claim 1 having the protruding portion joined to the hole,

While holding the plate material with one electrode, the fastening member is held with another electrode, energizing between the two members to generate electric resistance heat at the joint portion of the two members, and pressing the both members together A press-fit joint structure characterized in that the joint is formed in a solid-phase state by joining the joints while forming a joint interface therebetween.

[3] A base, a screw hole penetrating through the center of the base, and a cylindrical projection protruding from the periphery of the screw hole, and solid-phase bonded to the hole provided in the plate by press-fitting with electric resistance heat And a nut for press-fit joining, characterized in that it has a projecting portion having a predetermined press-fit allowance formed with a cross-section similar to the hole.

[4] The press-fit joining nut according to claim 3, wherein the back surface portion of the base portion is provided with a barrier housing portion that is formed so as to surround the protruding portion and is formed of an annular groove portion. .

[5] A base portion provided with a screw hole in the center portion, a flange portion formed integrally with the base portion on the back surface side of the base portion and provided with a hole portion continuous with the screw hole in the center, and a flange portion of the flange portion Projected in a cylindrical shape from the periphery of the hole, solid-phase bonded to the hole provided in the plate by press-fitting with electrical resistance heat, and formed a cross-section with a shape similar to that of the parenthesis to form a predetermined press-fitting allowance And a projecting portion provided with a nut for press-fit joining.

6. The nut for press-fit joining according to claim 5, wherein a groove-shaped burr storage portion surrounding the protruding portion is provided on the back surface portion of the flange portion.

[7] The thickness of the outer end portion of the flange portion is about 1. Omm, and the entire seating surface on the back surface of the flange portion is formed in a concave spherical shape. Or a nut for press-fit joining described in Item 6.

[8] The wall thickness of the above projecting part should be 1. Omm or more, and the projecting height width of the projecting part should be

The nut for press-fit joining according to any one of claims 3 to 7, wherein the nut is in a range of about 0.5 mm to 2. Omm.

[9] The joining structure of the plate according to any one of claims 3 to 8, which has a plate provided with a hole at a predetermined position and the protruding portion joined to the hole. The plate is held by one electrode, while the nut is held by another electrode, and an electric current is generated between the two members to generate electrical resistance heat at the joint between them, and by press-fitting. A press-fit joint structure characterized in that a joint interface is formed between the two members and the parentheses are joined in a solid phase.

[10] The press-fit joint structure according to item 9 of the claim, wherein the plate is made of high-strength steel or surface-treated steel.

[11] The press-fit joint structure according to [9] or [10], wherein a protruding height width of the protruding portion is equal to or smaller than a plate thickness of the plate.

[12] In a bolt having a head portion and a shaft portion provided with a screw groove, an enlarged portion having a larger diameter than the shaft portion is formed between the head portion and the shaft portion, and a hole provided in the panel. A predetermined press-fitting allowance is provided between the portion and the enlarged-diameter portion, and the enlarged-diameter portion is solid-phase joined to the hole portion by press-fitting with electrical resistance heat between them. Bolts.

[13] The diameter of the enlarged diameter part is formed to be larger than the diameter of the shaft part by 1 mm or more, and the height width of the enlarged diameter part is in the range of about 1 mm to 5 mm. The bolt for press-fit joining described in the section.

14. The press-fitting bolt according to claim 12 or 13, wherein a groove-shaped burr storage portion surrounding the enlarged diameter portion is provided on the back surface portion of the head portion.

[15] The bolt for press-fit joining according to any one of claims 12 to 14, wherein a high-tensile steel material is used as a constituent material.

[16] Joining a panel provided with a hole at a predetermined position and the bolt according to any one of claims 12 to 15 having the above-mentioned enlarged diameter part joined to the hole. The structure holds the panel with one electrode, while holding the bolt with another electrode, energizes between these two members to generate electrical resistance heat at the joint, and press fit A press-fit joint structure characterized in that a joint interface is formed between the two members and the parentheses are joined in a solid-phase state.

17. The press-fit joint structure according to claim 16, wherein a height width of the enlarged diameter portion is formed to be equal to or smaller than a plate thickness of the panel.

[18] The press-fit joint structure according to claim 16 or 17, wherein the panel is made of high-strength steel or surface-treated steel.