JP2022154579A - Fastening body and joint structure and joint method using the same - Google Patents

Abstract

To provide a fastening body which may easily deform into a desired shape when press-fitting into a friction stirring part to improve joint strength of a joint structure using the fastening body.SOLUTION: A fastening body (1) is press-fitted from the first member 41 side into a friction stirring part 50 formed at an overlapping part 45 between a first member 41 and a second member 42. The fastening body (1) includes: a head part 11 disposed on a surface of the friction stirring part 50; and a cylindrical shaft part 42 extending from the head part 11 to the second member 42 side. The shaft part 12 has a facilitation part (15) which facilitates expansion of a diameter of a tip part 12a of the shaft part 12 during the press-fitting.SELECTED DRAWING: Figure 2

Description

The present invention provides a fastening body that is press-fitted from the first member side into the friction stirring part in the first member and the second member that are joined via the friction stirring part, and a joined structure and joining using the fastening body Regarding the method.

2. Description of the Related Art When manufacturing a structure such as an aircraft, a railroad vehicle, or an automobile, it may be necessary to superimpose and join two or more members made of metal, resin, or the like. Joining using a rivet (fastening body) is known as one method of joining.

For example, Patent Literature 1 below discloses joining two or more resin members by a method that uses both rivets and thermal fusion. Specifically, in Patent Document 1, a step of stacking two thermoplastic resin members vertically and placing a conductive metal plate between them, and energizing and heating the placed metal plate to each resin Both resin members are joined by a method including the steps of: fusing the member and the metal plate; and driving (pressing) a rivet so as to penetrate the upper resin member and the metal plate.

JP 2013-002505 A

The joining method of Patent Literature 1 has the problem that it tends to increase the weight and the manufacturing cost because it is necessary to separately dispose a conductive metal plate between the resin members. Therefore, it is proposed to adopt friction stir welding as an alternative method that can solve the problem. Friction stir welding is a method of joining two or more members by friction stirring in which a rotating tool is pressed into an object to be welded. According to this joining method using both friction stir welding and riveting, the conductive metal plate is no longer an essential element, so it is possible to reduce the weight and manufacturing cost.

According to the joining method described above, the rivet is press-fitted into the friction-stirred region, which is the friction-stirred region. However, in this case, there is a possibility that the tip of the rivet will not expand as expected during press-fitting, and the required joint strength will not be obtained.

The present invention has been made in view of the above circumstances, and provides a fastening body that can be easily deformed into a desired shape when it is press-fitted into a friction stirrer, thereby providing a joint structure using the fastening body. The purpose is to improve the bonding strength of

In order to solve the above problems, a fastening body according to one aspect of the present invention is a friction stirrer formed by press-fitting a rotating tool from the first member side into an overlapping portion of a first member and a second member. A fastening body press-fitted from the first member side into the portion, the fastening body having a head portion arranged on the surface of the friction stirring portion, and a tubular shaft portion extending from the head portion toward the second member side. In addition, the shaft portion has a promoting portion that promotes the diameter expansion of the distal end portion of the shaft portion during press-fitting.

A joined structure according to another aspect of the present invention includes the first member and the second member, the friction stir portion formed in an overlapping portion of the first member and the second member, and the friction stir and the fastening body press-fitted into the part.

A joining method according to still another aspect of the present invention is a method of joining the first member and the second member using the fastening body, wherein the overlapping portion of the first member and the second member a friction stirring step of forming the friction stirring portion in the overlapping portion by performing friction stirring in which the rotating tool is press-fitted from the first member side to the friction stirring portion; and a fastening step of press-fitting.

As described above, according to the present invention, it is possible to provide a fastening body that can be easily deformed into a desired shape when it is press-fitted into a friction stirring part, and the bonding strength of a bonded structure using the fastening body can be increased. can be improved.

It is a sectional view showing the rivet concerning one embodiment of the present invention alone. FIG. 10 is a diagram showing a state in which the rivet is driven (press-fitted) into the object to be joined, and is a cross-sectional view showing the structure of a joint structure obtained by driving the rivet. FIG. 2 is a schematic diagram showing the overall configuration of a friction stir welding apparatus used when manufacturing the joined structure; It is sectional drawing which shows the 1st process (preparatory process) which manufactures the said joining structure. It is sectional drawing which shows the 2nd process (positioning process) which manufactures the said joining structure. FIG. 10 is a cross-sectional view showing a third process (friction stirring process) of manufacturing the joined structure; It is sectional drawing which shows the 4th process (placement process) which manufactures the said joining structure. 4 is a flowchart showing a procedure for judging pass/fail of bonding quality; It is a figure equivalent to FIG. 1 which shows the modification of the said embodiment.

[Rivet structure]
FIG. 1 is a sectional view showing a single rivet 1 according to one embodiment of the present invention. As shown in this figure, the rivet 1 is a fastening body that includes a disk-shaped head portion 11 and a cylindrical shaft portion 12 that extends concentrically from the head portion 11 . In this embodiment, the rivet 1 is a self-piercing rivet that is non-penetratingly driven into a material that does not have a pilot hole. In the following description, the head 11 side of the rivet 1 in the axial direction is referred to as "upper", and the shaft 12 side is referred to as "lower". It is not intended to be limiting.

The head 11 is formed in the shape of a solid disc that closes the opening at the upper end of the shaft 12 . Assuming that the outer diameter of the head portion 11 is R1 and the outer diameter of the shaft portion 12 is R2, the outer diameter R1 is set to a value larger than the outer diameter R2. Thereby, the head portion 11 is formed in a disc shape having a portion protruding radially outward from the upper end of the shaft portion 12 .

Shaft portion 12 is formed to extend vertically along the same axis as head portion 11 . The shaft portion 12 is a cylindrical body extending straight with a constant outer diameter smaller than that of the head portion 11, and has a hollow portion inside which is open on the side opposite to the head portion 11 (lower end side). Assuming that the total axial length (total length) of the rivet 1 including the shaft portion 12 and the head portion 11 is L, the total length L is a value sufficiently larger than the thickness (axial length) of the head portion 11. is set to

An end portion (lower end portion) of the shaft portion 12 opposite to the head portion 11, that is, a tip portion 12a is formed in a sharp shape. That is, the distal end portion 12a of the shaft portion 12 has a tapered inner peripheral surface 12s in which the inner diameter increases toward the distal end side (farther away from the head portion 11). The tip portion 12 a including the inner peripheral surface 12 s is also the opening edge of the tip (lower end) of the shaft portion 12 .

A concave groove 15 is formed in the middle portion of the outer peripheral surface of the shaft portion 12 in the axial direction (vertical direction). The concave groove 15 is a groove obtained by locally thinning the outer peripheral wall of the shaft portion 12, and has a predetermined concave shape such as a U-shape or a V-shape in a cross-sectional view. The groove 15 is formed on the outer peripheral surface of the shaft portion 12 so as to extend continuously in the circumferential direction. Assuming that the axial distance from the groove center of the groove 15 to the tip end position 12t of the shaft portion 12 is G, this distance G is the distance after the diameter of the shaft portion 12 is expanded when the rivet 1 is driven, which will be described later. It becomes a parameter that influences the shape.

The material of the rivet 1 can be selected from appropriate materials as long as it has a strength that allows it to be driven into the object to be joined. For example, a metal material such as titanium or high-strength steel, or a resin material such as thermoplastic resin or thermoplastic composite material can be used as the material of the rivet 1 . Note that when using the titanium rivet 1 for joining fiber-reinforced resin materials as in the present embodiment, a titanium alloy rivet such as Ti-6AL-4V is suitable.

[Structure of joined structure]
FIG. 2 is a diagram showing a state in which the rivet 1 is driven (press-fitted) into an object to be joined, and is a sectional view showing the structure of a joint structure 30 obtained by driving the rivet 1. FIG. As shown in this figure, the joint structure 30 includes a first member 41 and a second member 42 that overlap each other, a friction stirrer 50 formed in an overlapping portion 45 of the members 41 and 42, and a friction stirrer 50 and the above-mentioned rivet 1 driven in. Bonded structure 30 may be used, for example, in structures such as aircraft, rail vehicles, or automobiles.

The first member 41 and the second member 42 are both plate-shaped members, and are vertically stacked with the first member 41 facing upward (the second member 42 facing downward). The overlapping first member 41 and second member 42 form an overlapping portion 45 at a position where the frictional stirring portion 50 is to be formed.

Both the first member 41 and the second member 42 are made of a thermoplastic composite material. Specifically, the first member 41 and the second member 42 are made of a fiber-reinforced thermoplastic resin including a thermoplastic resin base material and a large number of reinforcing fibers impregnated in the base material. The thickness of the second member 42 may be the same as or different from the thickness of the first member 41 .

Thermoplastic resins that can be used as base materials for the first member 41 and the second member 42 include polypropylene (PP), polyethylene (PE), polyamide (PA), polystyrene (PS), polyaryletherketone (PEAK), ), polyacetal (POM), polycarbonate (PC), polyethylene terephthalate (PET), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), ABS resin, and thermoplastic epoxy resin. Examples of reinforcing fibers impregnated into the base material include carbon fibers, glass fibers, ceramic fibers, metal fibers, and organic fibers.

The friction-stirred portion 50 is a joint portion formed by hardening the material frictionally-stirred in the overlapping portion 45 . The friction stirrer 50 is formed in a columnar shape corresponding to a region into which a rotary tool 101 (to be described later) is press-fitted. That is, the friction stirrer 50 has a circular upper surface 50a and a circular bottom surface 50b, and a cylindrical side peripheral surface 50c. The upper surface 50 a is formed at a height position substantially flush with the upper surface 41 a of the first member 41 . The bottom surface 50b is formed at a position corresponding to the boundary between the frictional stirring portion 50 and the non-frictional stirring portion (base material region) below it. The side peripheral surface 50c is formed at a position corresponding to the boundary between the frictional stirring portion 50 and the non-frictional stirring portion (base material region) on the outer peripheral side thereof. The friction stirrer 50 does not necessarily have to reach the second member 42 on the lower side, but in this embodiment, the depth of the friction stirrer 50 reaches the second member 42 . is set to a value greater than the thickness of the

The rivet 1 is driven (press-fitted) into the friction stirrer 50 so as to mechanically join the first member 41 and the second member 42 . That is, the rivet 1 mechanically joins the first member 41 and the second member 42 by being driven into the overlapping portion 45 (frictional stirring portion 50) after the overlapping portion 45 has been frictionally stirred by a rotary tool 101, which will be described later. joints effectively. In this state after driving, the head 11 of the rivet 1 contacts the upper surface 50 a (surface) of the friction stirrer 50 . Further, by the driving, the shank 12 of the rivet 1 is changed into a tapered shape in which the outer diameter of the tip portion 12a is enlarged. Specifically, the shaft portion 12 after driving is arranged so as to pass through the first member 41 and extend halfway in the thickness direction of the second member 42, and the tip side (farther from the head portion 11) It is formed so that the outer diameter increases as much as possible). The distal end portion 12a of the shaft portion 12 in this state protrudes to the outside of the friction stirring portion 50 and functions as an interlock portion that fastens the first member 41 and the second member 42 together. That is, the first member 41 and the second member 42 are located between the interlock portion composed of the tip portion 12a projecting to the outside of the friction stirring portion 50 and the head portion 11 arranged on the upper surface 50a of the friction stirring portion 50. are fixed to each other by being sandwiched between the

[Friction stir welding equipment]
The joint structure 30 including the rivet 1 and the friction stir welding part 50 described above is manufactured using the friction stir welding apparatus M shown in FIG. As shown in the figure, the friction stir welding apparatus M includes a double-acting rotating tool 101, a tool driving unit 102 that drives the rotating tool 101 to rotate and move up and down, and a controller C that controls the operation of the tool driving unit 102. including. Note that FIG. 3 shows directions of “up” and “down”, but this is for convenience of explanation and is not meant to limit the actual usage posture of the rotating tool 101 .

The rotating tool 101 is supported by a tool fixing portion (not shown). This tool fixing part can be, for example, the tip part of an articulated robot. A backup member 115 is arranged facing the lower end surface of the rotary tool 101 . A first member 41 and a second member 42 to be joined are arranged between the rotary tool 101 and the backup member 115 .

Rotary tool 101 comprises pin member 111 , shoulder member 112 , clamp member 113 and spring 114 . The pin member 111 is a columnar member, and is arranged so that its axis extends in the vertical direction. The pin member 111 can rotate about the axis R as the rotation axis R, and can move up and down (advance and retreat) along the rotation axis R in the vertical direction.

Shoulder member 112 is arranged to cover the outer periphery of pin member 111 . That is, the shoulder member 112 is a cylindrical member having a hollow portion into which the pin member 111 is inserted. The axis of the shoulder member 112 is coaxial with the axis of the pin member 111 (rotational axis R). The shoulder member 112 rotates around the same rotation axis R as the pin member 111 and can move vertically along the rotation axis R (movement back and forth). Thus, both the shoulder member 112 and the pin member 111 inserted in the hollow portion thereof can rotate about the rotation axis R and relatively move along the rotation axis R. That is, the pin member 111 and the shoulder member 112 can move not only up and down simultaneously along the rotation axis R, but also move independently such that one moves down and the other moves up.

The clamp member 113 is arranged so as to cover the outer circumference of the shoulder member 112 . That is, the clamp member 113 is a cylindrical member having a hollow portion into which the shoulder member 112 is inserted. The axis of the clamp member 113 is also coaxial with the rotation axis R. The clamp member 113 does not rotate about its axis, but can move up and down (advance and retreat) along the rotation axis R. As shown in FIG. The clamp member 113 serves to surround the outer periphery of the pin member 111 or the shoulder member 112 when performing friction stirring. The enclosure of the clamp member 113 prevents the frictional stirring material from scattering and allows the frictional stirring portion to be smoothly finished.

A spring 114 is attached to the upper end side of the clamp member 113 and biases the clamp member 113 in a direction (downward) toward the object to be joined. A clamp member 113 is attached to the tool fixing portion via a spring 114 .

The backup member 115 has an upper surface (support surface) that contacts the lower surface of the object to be joined. That is, the backup member 115 is a backing member that supports the object to be welded when the pin member 111 or the shoulder member 112 is press-fitted into the object to be welded. A clamp member 113 biased by a spring 114 presses the object to be joined against a backup member 115 .

Tool drive 102 includes rotary drive 121 , pin drive 122 , shoulder drive 123 and clamp drive 124 . The rotation drive unit 121 is a mechanism that rotates the pin member 111 and the shoulder member 112 around the rotation axis R. As shown in FIG. The pin drive unit 122 is a mechanism that advances and retreats (lifts) the pin member 111 along the rotation axis R. As shown in FIG. The pin drive unit 122 drives the pin member 111 so as to press-fit the pin member 111 into the object to be joined and retract from the object to be joined. The shoulder drive unit 123 is a mechanism that advances and retreats the shoulder member 112 along the rotation axis R, and causes the shoulder member 112 to be press-fitted into and retracted from the object to be joined. The clamp drive unit 124 is a mechanism that advances and retreats the clamp member 113 along the rotation axis R. As shown in FIG. The clamp drive unit 124 moves the clamp member 113 toward the object to be welded and presses the object to be welded against the backup member 115 . At this time, the biasing force of the spring 114 acts. Each drive unit 121 to 124 includes a servomotor, a transmission gear, and the like, and causes each driven object to perform a desired operation according to the rotation of the servomotor.

The controller C is composed of a microcomputer or the like, and controls the operation of each part of the tool driving section 102 by executing a predetermined control program. Specifically, the controller C controls the rotation driving section 121 to cause the pin member 111 and the shoulder member 112 to perform required rotation operations. In addition, the controller C controls the pin driving section 122, the shoulder driving section 123, and the clamp driving section 124 to cause the pin member 111, the shoulder member 112, and the clamp member 113 to move forward and backward as required.

The friction stir welding apparatus M having the structure described above is usually used for joining two or more members by friction stir welding. Friction stir welding using this friction stir welding apparatus M can be broadly classified into a welding method by a shoulder-first process and a welding method by a pin-first process.

In the shoulder-preceding process joining method, the shoulder member 112 of the rotating tool 101 is first press-fitted into the overlapped portion of the two or more members to perform friction stirring, and the pin member 111 is retracted from the overlapped portion. Thereafter, the pin member 111 is lowered while retracting (raising) the shoulder member 112, thereby smoothing the upper surface of the overlapping portion. On the other hand, in the joining method by the pin precedence process, the pin member 111 of the rotary tool 101 is first press-fitted into the overlapping portion to perform friction stirring, and the shoulder member 112 is retracted from the overlapping portion. After that, the shoulder member 112 is lowered while the pin member 111 is retracted (raised), thereby smoothing the upper surface of the overlapping portion.

[Joining method]
Next, a method for joining the first member 41 and the second member 42 using the friction stir welding apparatus M described above will be described in detail. When joining the first member 41 and the second member 42 in the present embodiment, riveted friction stir welding combining driving of the rivets 1 and friction stir welding is used. Friction stir welding combined with rivets differs from normal friction stir welding in that rivets are added as a joining means. It is possible to realize friction stir welding with riveting using only the device M (without adding another device for driving the rivet 1). That is, when the first member 41 and the second member 42 are joined together, the shoulder member 112 of the rotary tool 101 is press-fitted into the overlapped portion 45 of both to perform friction stirring, and the overlapped portion 45 ( A rivet 1 is driven into the friction stirrer 50) using a pin member 111. As shown in FIG. Thereby, the joined structure 30 is manufactured by joining the first member 41 and the second member 42 . Specifically, the joining method of the first and second members 41 and 42 includes the following four steps P1 to P4.

Process P1 is a preparatory process for mounting the rivet 1 on the rotary tool 101, as shown in FIG. The rivet 1 attached to the rotary tool 101 in this preparation step P1 is the rivet 1 before being driven into the overlapping portion 45, and the shaft portion 12 has not yet been expanded. That is, the rivet 1 used in the preparation step P1 has a head portion 11 and a cylindrical shaft portion 12 extending straight from the head portion 11 .

In order to mount the rivet 1 on the rotary tool 101 , the controller C ( FIG. 3 ) drives the pin driving section 122 to raise the pin member 111 and create a receiving space V for the rivet 1 inside the shoulder member 112 . That is, the controller C lifts the tip (lower end) 111a of the pin member 111 with respect to the tip (lower end) 112a of the shoulder member 112 by a stroke equal to or greater than the total length L (FIG. 1) of the rivet 1, thereby lifting the shoulder member 112. A housing space V is formed that continues to the lower end opening. In order to accommodate the rivet 1 in the accommodation space V, the rivet 1 is selected to have an outer diameter slightly smaller than the inner diameter of the shoulder member 112 .

Step P2 is a positioning step of positioning the rotating tool 101 with the rivet 1 attached to the overlapping portion 45 in which the first member 41 and the second member 42 are stacked in order from above, as shown in FIG. . In this positioning step P2, the controller C positions the rotation axis R (FIG. 3) of the rotary tool 101 so that it coincides with the center of the overlapping portion 45 supported on the backup member 115, and then the shoulder member 112 and the clamp. The shoulder driving portion 123 and the clamp driving portion 124 are controlled so that the tips 112 a and 113 a of the member 113 come into contact with the upper surface 41 a of the first member 41 . Further, the controller C controls the axial relative positional relationship between the pin member 111 and the shoulder member 112 (pin The tip 111a is retracted upward by a predetermined amount with respect to the shoulder tip 112a).

Process P3 is a friction stirring process in which the shoulder member 112 is press-fitted while being rotated, as shown in FIG. In this friction stirring step P3, the controller C controls the rotation drive unit 121 to rotate the pin member 111 and the shoulder member 112 at high speed, while controlling the shoulder drive unit 123 to lower the shoulder member 112 and 112 is press-fitted into the overlapping portion 45 . Further, the controller C controls the pin drive section 122 to raise the pin member 111 . Due to this operation, the overlapping portion 45 is frictionally agitated, softening and plastic flow of the material occur, and the softened material Q1 overflows the press-fit region of the shoulder member 112 . The overflowed softened material Q1 is released into the hollow space inside the shoulder member 112 created by the upward movement (retraction) of the pin member 111 (see arrow b1). At the start of the friction stirring step P3, the pin members 111 are already retracted upward to the extent that the accommodation space V (FIG. 4) is formed, so the retracting operation of the pin members 111 may be omitted.

Assuming that the press-fitting depth of the shoulder member 112 is h1, the press-fitting depth h1 is set to a value such that the shoulder member 112 penetrates at least the upper first member 41 . In this embodiment, an example is shown in which the press-fit depth h1 is set to a value such that the shoulder member 112 penetrates the first member 41 on the upper side and does not penetrate the second member 42 on the lower side. In other words, the press-fit depth h1 in this embodiment is larger than the thickness t1 of the first member 41 and smaller than the sum (t1+t2) of the thickness t1 and the thickness t2 of the second member 42. is set to

In this embodiment, since the first member 41 and the second member 42 are thermoplastic composite materials, the material Q1 softened by the friction stirring contains reinforcing fibers. However, the reinforcing fibers in this softening material Q1 are finely cut by friction stirring. This facilitates subsequent setting of the rivet 1 .

Step P4 is a step of driving the rivet 1 into the overlapping portion 45, as shown in FIGS. 7(a) and 7(b). In this placing step P4, the controller C controls the rotation drive section 121 to rotate the pin member 111 and the shoulder member 112 at high speed, and controls the shoulder drive section 123 to raise the shoulder member 112 . Further, following the rise of the shoulder member 112, the controller C controls the pin drive section 122 to lower the pin member 111. As shown in FIG. By this operation, a columnar frictional stirrer 50 is formed in the overlapped portion 45 and the rivet 1 is driven in a region including the frictional stirrer 50 . Formation of the friction stirrer 50 and driving of the rivet 1 will be described in detail below.

First, the formation of the friction stirrer 50 by the placing step P4 will be described. In the placing step P4, the shoulder member 112 is raised and the pin member 111 is lowered, so that the softened material Q1 (FIG. 6) released into the hollow space is moved to the area where the shoulder member 112 was press-fitted. and material backfilling. The backfilled material forms a friction stirrer 50 in the overlapping portion 45 together with the material that was present in the hollow space. The friction stirrer 50 is made of a material that has undergone friction stirrer in the overlapping portion 45, and has an outer diameter Sr that substantially matches the outer diameter ds (FIG. 7B) of the shoulder member 112 and the press-fit depth of the shoulder member 112. It is formed in a columnar shape with a height Sd substantially matching h1 (FIG. 6). That is, the friction stirrer 50 has a cylindrical side peripheral surface 50c with a height Sd (≈h1) and circular top and bottom surfaces 50a and 50b with an outer diameter Sr (≈ds). While the material is softened in the friction stirrer 50, in the base material region around the friction stirrer 50, the original hardness of the first member 41 and the second member 42 is maintained, and the reinforcing structure by the reinforcing fibers is also maintained. It is

Next, driving of the rivet 1 in the driving step P4 will be described. In the driving step P<b>4 , the rivet 1 is pressed downward as the pin member 111 descends, and the pressed rivet 1 is pushed into the overlapping portion 45 . In other words, in the driving step P4, the rivet 1 is driven using an existing part (the pin member 111) of the rotary tool 101. As shown in FIG. Therefore, in the present embodiment, it is possible to form a joint formed by a combination of the rivet 1 and the friction stirrer 50 in the overlapping portion 45 without separately preparing a tool for driving the rivet 1 .

Specifically, in the driving step P4, the pin driving portion 122 lowers the pin member 111 to apply a pressing force to the head portion 11 of the rivet 1, thereby pushing the rivet 1 into the overlapping portion 45 (see FIG. 7(a)). . The rivet 1 is previously loaded in the housing space V (FIG. 4) so that the top surface of the head 11 faces the tip 111a of the pin member 111. As shown in FIG. Therefore, when the pin member 111 descends, the rivet 1 also descends, and the shaft portion 12 enters into the frictional stirring portion 50 from the tip side. As the rivet 1 advances (presses down the pin member 111 ), the tip 12 a of the shaft portion 12 eventually reaches the bottom surface 50 b of the friction stirrer 50 .

Here, since the area below the bottom surface 50b is an unsoftened base material area, when the tip portion 12a reaches the bottom surface 50b, the axial resistance acting on the shaft portion 12 increases. Therefore, at least when the tip portion 12a reaches the bottom surface 50b, a force acts on the shaft portion 12 to expand the diameter of the tip portion 12a. The generation of such a diameter-expanding force is facilitated by the tapered inner peripheral surface 12s formed on the distal end portion 12a. That is, due to the synergistic effect of the increased resistance due to the tip portion 12a reaching the bottom surface 50b and the tapered shape of the inner peripheral surface 12s of the tip portion 12a, a large force for expanding the diameter of the tip portion 12a of the shaft portion 12 is generated. works. The shaft portion 12 that receives this diameter-expanding force undergoes buckling deformation starting from the concave groove 15 formed on the outer peripheral surface of the shaft portion 12. As a result, the shaft portion 12 expands forward as shown in FIG. It deforms and the outer diameter of the tip portion 12a expands. In other words, the concave groove 15 functions as an acceleration portion that promotes the diameter expansion of the tip portion 12a of the shaft portion 12 when the shaft portion 12 is press-fitted (when the rivet 1 is driven).

FIG. 7(b) shows a state in which the head 11 of the rivet 1 has reached the upper surface of the overlapping portion 45 (the upper surface 50a of the friction stirrer 50), that is, the state in which the driving of the rivet 1 is completed. As shown in this figure, when the driving of the rivet 1 is completed, the tip portion 12a of the shaft portion 12 is not only press-fitted beyond the bottom surface 50b of the friction stirrer 50 into the base material region below it, The friction stirrer 50 is also press-fitted beyond the side peripheral surface 50c into the outer base material region. The tip portion 12a press-fitted to the outside of the friction stirrer 50 in this way exerts an anchoring effect against the force separating the first member 41 and the second member 42 from each other. That is, the distal end portion 12a functions as an interlock portion that fastens the first member 41 and the second member 42 together.

Through the steps P1 to P4 described above, the frictional stirring portion 50 is formed in the overlapping portion 45 and the rivet 1 is driven. The combination of the rivet 1 and the friction stirrer 50 joins the first member 41 and the second member 42 relatively firmly at the overlapping portion 45 .

[Admission decision]
Next, a method for confirming whether or not the rivet 1 has been properly set when the first and second members 41 and 42 are joined by the above-described joining method, that is, a method for judging whether or not the joining quality of the rivet 1 is acceptable will be described. do. FIG. 8 is a flow chart showing a specific procedure for this acceptance/rejection determination. The control shown in this figure is executed by the controller C in parallel with the main control of friction stir welding with riveting shown in FIGS. When the control in FIG. 8 starts, the controller C acquires the dimensions of each part of the rivet 1 (step S1). Specifically, the controller C acquires the total length L of the rivet 1 shown in FIG. 1, the outer diameter R2 of the shaft portion 12, and the distance G representing the axial position of the groove 15, respectively. These dimensions are stored in advance in a storage unit built in the controller C. FIG.

Next, the controller C performs friction stirring for press-fitting the rotating tool 101 into the overlapping portion 45 (step S2). That is, the controller C rotates the shoulder member 112 at high speed and press-fits it into the overlapping portion 45 (see FIG. 6), and then raises (retracts) the shoulder member 112 so that the frictional stirring portion 50 (see FIG. (a)) is formed.

Next, the controller C obtains the outer diameter Sr (FIG. 7(b)) of the friction stirrer 50 (step S3). Hereinafter, the outer diameter Sr of the friction stirrer 50 is abbreviated as the friction stirrer diameter Sr. The friction stirring diameter Sr is stored in advance in the storage section as a value substantially matching the outer diameter ds of the shoulder member 112 .

Next, the controller C calculates the height Sd of the friction stirrer 50 (step S4). Hereinafter, the height Sd of the friction stirrer 50 is abbreviated as the friction stirrer depth Sd. The frictional agitation depth Sd can be calculated, for example, based on an output value from an encoder built into the servomotor of the shoulder driving section 123 . That is, the controller C calculates the axis value (vertical coordinate) of the shoulder member 112 when friction stirring is started and the axis value when the shoulder member 112 descends most during friction stirring from the output value of the encoder. The difference between the specified axial values, that is, the depth of press-fitting of the shoulder member 112 into the overlapping portion 45 is calculated as the frictional stirring depth Sd.

Next, the controller C drives the rivet 1 into the friction stirrer 50 (step S5). That is, the controller C lowers the pin member 111 to push down the rivet 1, thereby press-fitting the shaft portion 12 of the rivet 1 into the friction stirrer 50 (see FIG. 7(b)).

Next, the controller C calculates the protrusion amount H of the head 11 from the upper surface 50a of the friction stirrer 50 (step S6). For example, the controller C determines the shaft value and the shoulder value of the pin member 111 at the point in time in FIG. The axial value of the member 112 is specified, and the difference between the specified axial values is calculated as the protrusion amount H of the head 11 .

Next, the controller C estimates the tip diameter Rd, which is the outer diameter of the tip portion 12a of the shaft portion 12 (step S7). Specifically, the controller C determines the dimensions of the rivet 1 acquired in step S1 (the total length L of the rivet 1, the outer diameter R2 of the shaft portion 12, the distance G representing the axial position of the groove 15), and the step The tip diameter Rd of the shaft portion 12 is estimated based on the friction stirring depth Sd calculated in S4 and the protrusion amount H of the head portion 11 calculated in step S6. That is, the tip diameter Rd of the shaft portion 12 after driving the rivet 1 is the diameter expansion of the shaft portion 12 caused in the process of the shaft portion 12 being press-fitted into the friction stirrer 50, particularly , the tip diameter Rd is determined by the size of the rivet 1 (overall length L and outer diameter R2) and the axial position of the groove 15 (distance G ) and the friction stirring depth Sd. Also, the amount of protrusion H of the head 11 changes depending on whether the rivet 1 has been driven properly. Insufficient driving also deviates the tip diameter Rd described above. From the above circumstances, in step S7, the tip diameter Rd is estimated based on the parameters L, R2, G, Sd, and H described above. For this estimation, for example, a model calculation formula predetermined by experiments or the like can be used.

Next, the controller C determines whether or not the tip diameter Rd of the shaft portion 12 estimated in step S7 is larger than the friction stirring diameter Sr obtained in step S3 (step S8).

If the determination in step S8 is YES and it is confirmed that the tip diameter Rd is larger than the friction stirring diameter Sr, the controller C determines that the driving (press-fitting) of the rivet 1 has been properly performed, Predetermined processing such as providing the result of the determination (OK determination) to the operator is performed (step S9). That is, the fact that the tip diameter Rd is larger than the friction stirring diameter Sr (Rd>Sr) means that the tip portion 12a of the shaft portion 12 bites into the base material region outside the friction stirring portion 50, that is, the interlock portion is properly formed. Formation of such an interlock portion suggests that the quality of joining by the rivet 1 is good. Therefore, the controller C presents an OK determination in step S9.

On the other hand, if the determination in step S8 is NO and it is confirmed that the tip diameter Rd is equal to or smaller than the friction stirring diameter Sr, the controller C assumes that the rivet 1 was not properly driven (press-fitted). Then, predetermined processing such as providing the result of the determination (NG determination) to the operator is performed (step S10). That is, the fact that the tip diameter Rd is equal to or less than the friction stirring diameter Sr (Rd≦Sr) means that the tip portion 12a of the shaft portion 12 does not bite into the outer base material region of the friction stirring portion 50, that is, the formation of the interlock portion. is not achieved. The non-formation of such an interlock portion suggests that the joint quality by the rivet 1 is poor. Therefore, the controller C presents an NG judgment in step S10.

[Effect]
As described above, in the present embodiment, when the first member 41 and the second member 42 are joined together, the overlapping portion 45 of both is friction-stirred by the rotating tool 101, and the friction-stirring portion 50 formed thereby Since the rivet 1 is further press-fitted to the joint, the first member 41 and the second member 42 can be joined with sufficient strength by the combination of the friction stirrer 50 and the rivet 1 .

In particular, since the rivet 1 used in the present embodiment includes the shaft portion 12 in which the groove 15 extending in the circumferential direction is formed on the outer peripheral surface, the groove 15 is formed when the rivet 1 is press-fitted into the friction stirrer 50. The tip portion 12a of the shaft portion 12 can be easily expanded in diameter by buckling the shaft portion 12 at the starting point. As a result, it is possible to obtain with a high probability a state in which the tip portion 12a of the shaft portion 12 bites into the base material region outside the friction stirrer 50, and the interlock portion formed by the tip portion 12a that has bitten into the base material region can be obtained. The function allows the first member 41 and the second member 42 to be mechanically properly joined. This enables the first member 41 and the second member 42 to be joined with sufficient strength in combination with the joining by the friction stirrer 50, thereby improving the joining quality.

Here, in the present embodiment, as means (promoting portion) for promoting diameter expansion of the shaft portion 12, the concave groove 15 formed by locally thinning the outer peripheral wall of the shaft portion 12 is used. Depending on the depth of the recessed groove 15, the load capacity of the rivet 1 itself may be significantly reduced. In other words, if the depth of the recessed groove 15 is excessively increased, even if the interlock portion can be reliably obtained, there is a possibility that the amount of improvement in the bonding strength will be limited. For this reason, it is desirable to make the depth of the groove 15 as small as possible within the range where the effect of promoting the diameter expansion to the extent necessary for forming the interlock portion can be obtained. In other words, it is desirable to determine the depth of the groove 15 to a value that allows the promotion of diameter expansion of the shaft portion 12 and the withstand load (or joint strength) of the rivet 1 to be well balanced.

Further, in the present embodiment, since the tapered inner peripheral surface 12s (the inner diameter increases toward the tip end) is formed at the distal end portion 12a of the shaft portion 12, the resistance force acting on the shaft portion 12 when the rivet 1 is press-fitted is formed. can be converted into a diameter-expanding force via the tapered inner peripheral surface 12s. This leads to a synergistic effect with the action of the recessed groove 15 described above, thereby sufficiently promoting the expansion of the diameter of the distal end portion 12a. Thereby, the probability that the interlock portion is formed can be increased, and the joining quality can be sufficiently improved.

Further, in the present embodiment, each dimension (L, R2, G in FIG. 1) of the rivet 1 before press-fitting, the friction stirring depth Sd which is the depth of the friction stirring portion 50, and the upper surface 50a of the friction stirring portion 50 The tip diameter Rd of the shaft portion 12 after press-fitting is estimated based on the projection amount H of the head portion 11 of the rivet 1 relative to the rivet 1, and the estimated tip diameter Rd and a predetermined threshold value (here, the friction stirrer 50 The acceptance or rejection of the joining quality is determined based on a comparison with the friction stirring diameter (Sr), which is the outer diameter. With such a configuration, it is possible to ensure the joining quality of the rivet 1 by a simple method that does not require a special inspection device (for example, an inspection device using X-rays, thermography, etc.).

In particular, in this embodiment, as one of the dimensional parameters for estimating the tip diameter Rd of the shaft portion 12, the distance G (FIG. 1) representing the axial position of the groove 15 is used. An appropriate estimated value of the tip diameter Rd can be obtained in consideration of the phenomenon in which the shaft portion 12 buckles starting from , and the estimation accuracy of the tip diameter Rd can be improved.

[Modification]
In the above-described embodiment, the concave groove 15 is formed in the outer peripheral surface of the shaft portion 12 as a means for promoting the diameter expansion of the tip portion 12a of the shaft portion 12 of the rivet 1, that is, as a promotion portion. It is not limited to the concave groove 15 as long as it can promote the expansion of the diameter of the groove 12a. For example, as shown in FIG. 9, it is possible to provide a reduced thickness portion 65 formed by reducing the thickness of both the inner peripheral wall and the outer peripheral wall in the middle of the shaft portion 12 so that the reduced thickness portion 65 functions as a promotion portion. is. Although not shown in the drawings, the shaft portion 12 is divided into a first portion and a second portion arranged in the axial direction, and the first portion and the second portion are formed by using a relatively low-strength welding metal or the like. You may make it join coaxially. With this configuration, the joint portion (welded portion) between the first portion and the second portion can function as an facilitating portion.

In the above-described embodiment, the first member 41 and the second member 42 are directly overlapped and joined together, but the first member 41 and the second member 42 are joined together with one or more other members interposed therebetween. The first member 41 and the second member 42 may be joined together.

In the above embodiment, both the first member 41 and the second member 42 are made of a thermoplastic composite material that includes a thermoplastic resin base material and a large number of reinforcing fibers impregnated in the base material. The materials of the first member 41 and the second member 42 may be different from each other. For example, one of the first member 41 and the second member 42 may be a thermoplastic resin molding, and the other may be a fiber-reinforced composite molding. Alternatively, one of the first member 41 and the second member 42 may be a molded body of metal and the other may be a molded body of a different metal or thermoplastic resin.

[summary]
The above-described embodiments and modifications thereof mainly include the following inventions.

A fastening body according to one aspect of the present invention is press-fitted from the first member side into a friction stirrer portion formed by press-fitting a rotating tool from the first member side into the overlapped portion of the first member and the second member. The fastening body includes a head arranged on the surface of the friction stirrer, and a tubular shaft extending from the head toward the second member, and the shaft is press-fitted. It has a promoting portion that promotes the diameter expansion of the distal end portion of the shaft portion.

ADVANTAGE OF THE INVENTION According to this invention, when press-fitting a fastening body to a friction stirring part, the axial part of the fastening body can be buckled from the promotion|promotion part as a starting point, and the front-end|tip part of the said axial part can be expanded easily. As a result, it is possible to obtain a state with a high probability that the tip of the shaft part has bitten into the base material area outside the friction stirrer, and the interlock part made up of the tip part that has bitten into the base material area can be used to weld the object. can be properly joined mechanically. This, in combination with the welding by the friction stirrer, makes it possible to weld the objects to be welded with sufficient strength and improve the welding quality.

The facilitating portion may be, for example, a concave groove extending in the circumferential direction formed on the outer peripheral surface of the shaft portion.

According to this configuration, it is possible to facilitate the expansion of the diameter of the distal end portion of the shaft portion with a simple configuration in which the groove is provided on the outer peripheral surface of the shaft portion. Further, by adjusting the depth of the concave groove, it is possible to achieve a good balance between acceleration of diameter expansion of the shaft portion and load resistance (or joint strength) of the fastening body.

Preferably, the distal end portion of the shaft portion has a tapered inner peripheral surface whose inner diameter increases toward the distal end side.

According to this configuration, the resistance force acting on the shaft portion when the fastening body is press-fitted is converted into a diameter-expanding force via the tapered inner peripheral surface. , the diameter expansion of the tip portion can be sufficiently promoted. Thereby, the probability that the interlock portion is formed can be increased, and the joining quality can be sufficiently improved.

A joined structure according to another aspect of the present invention includes the first member and the second member, the friction stir portion formed in an overlapping portion of the first member and the second member, and the friction stir and the fastening body press-fitted into the part.

The joint structure of the present invention has sufficient joint strength based on the combination of the fastening body and the friction stirrer.

A joining method according to still another aspect of the present invention is a method of joining the first member and the second member using the fastening body, wherein the overlapping portion of the first member and the second member a friction stirring step of forming the friction stirring portion in the overlapping portion by performing friction stirring in which the rotating tool is press-fitted from the first member side to the friction stirring portion; and a fastening step of press-fitting.

According to the joining method of the present invention, it is possible to obtain a joined structure having sufficient joining strength based on the combination of the fastening body and the friction stir portion.

The joining method preferably has a dimension before press-fitting of the fastening body, a friction stirring depth in the friction stirring step, and a protrusion amount of the head from the upper surface of the friction stirring part after the fastening step. estimating the tip diameter of the shaft portion after the fastening step based on the above, and determining that good joining has been performed when the estimated tip diameter is larger than a predetermined threshold.

According to this configuration, it is possible to ensure the joint quality of the fastening body by a simple method that does not require a special inspection device (for example, an inspection device using X-rays, thermography, etc.).

The dimensions before press fitting may include, for example, the axial length of the fastener, the outer diameter of the shank, and the distance representing the axial position of the facilitating portion.

According to this configuration, it is possible to obtain an appropriate tip diameter estimation value in consideration of the phenomenon in which the shaft portion buckles starting from the promoting portion, and it is possible to improve the estimation accuracy of the tip diameter.

1: Rivet (fastening body)
Reference Signs List 11: Head 12: Shaft 12a: Tip (of shaft) 12s: (Tapered) inner peripheral surface 15: Groove (promoting portion)
30: Joined structure 41: First member 42: Second member 45: Overlapping portion 50: Friction stirrer 50a: Upper surface (of friction stirrer) 65: Thinned portion (promoting portion)
L: Total length (of the rivet) R2: Outer diameter (of the shank) G: Distance (indicating the axial position of the concave groove) H: Projection amount (of the head) Sd: Friction stir depth Sr: Friction stir diameter (threshold)
Rd: Tip diameter (of shaft)

Claims (7)

A fastening body press-fitted from the first member side into a friction stirrer portion formed by press-fitting a rotating tool from the first member side into an overlapping portion of the first member and the second member,
a head arranged on the surface of the friction stirrer;
a cylindrical shaft extending from the head toward the second member;
The fastening body, wherein the shaft portion has a promoting portion that promotes diameter expansion of the tip portion of the shaft portion during press-fitting. In the fastening body according to claim 1,
The fastening body, wherein the facilitating portion is a groove extending in the circumferential direction formed on the outer peripheral surface of the shaft portion. In the fastening body according to claim 1 or 2,
A fastening body, wherein a distal end portion of the shaft portion has a tapered inner peripheral surface whose inner diameter increases toward the distal end side. the first member and the second member;
the friction stirrer formed in an overlapping portion of the first member and the second member;
A joined structure comprising the fastening body according to any one of claims 1 to 3 press-fitted into the friction stirrer. A method for joining the first member and the second member using the fastening body according to any one of claims 1 to 3,
A friction stirring step of forming the friction stirring portion in the overlapping portion by performing friction stirring by press-fitting the rotating tool into the overlapping portion of the first member and the second member from the first member side;
and a fastening step of press-fitting the fastening body into the friction stirrer from the side of the first member. In the joining method according to claim 5,
Based on the dimensions before press-fitting of the fastening body, the depth of friction stirring in the friction stirring step, and the amount of protrusion of the head from the upper surface of the friction stirring part after the fastening step, after the fastening step The joining method further includes a determination step of estimating a tip diameter of the shaft portion and determining that good joining has been performed when the estimated tip diameter is larger than a predetermined threshold. In the joining method according to claim 6,
The joining method, wherein the dimensions before press-fitting include the axial length of the fastening body, the outer diameter of the shaft portion, and the distance representing the axial position of the facilitating portion.

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