Friction stir welding apparatus and its maintenance method

Abstract

To reduce costs of components of a shoulder and maintenance costs.SOLUTION: A friction stir joining device M comprises: a pin 11 extending along a shaft line (R); a cylindrical shoulder 12 arranged concentrically with an outer periphery of the pin 11; and a driving part (3) that moves back and forth the pin 11 and the shoulder 12 along the shaft line (R) individually while rotating the pin and the shoulder around the shaft line (R). The shoulder 12 includes a shoulder main body 121 having a tip part (121a) that is press-fitted into an object (13) to be joined, and a shoulder adaptor 122 having a fitting hole H2 to which a base part (121b) of the shoulder main body 121 is fitted by shrinkage fit, which connects the shoulder main body 121 to the driving part (3).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a friction stir welding device including a pin body and a shoulder body.

Background Art

[0002] When manufacturing a structure such as an aircraft, a railway vehicle, or an automobile, an operation of overlapping and joining two or more members made of metal, resin, or the like may be performed. As one method of this joining, friction stir welding is known. Friction stir welding is a method of joining a workpiece by pressing a rotating tool into the workpiece (joining target) to generate plastic flow.

[0003] In Patent Document 1 below, as an example of a device for performing friction stir welding, a friction stir welding device including a pin (probe) capable of rotating around an axis and advancing and retreating along the axis, and a shoulder (shoulder member) disposed outside the pin and capable of rotating around the axis and advancing and retreating along the axis is disclosed. The pin and the shoulder are each press-fitted into the workpiece while being rotationally driven, and plastic flow is generated in the press-fitting portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, the shoulder integrally has a small-diameter and thin-walled cylindrical shoulder tip portion and a large-diameter and thick-walled cylindrical shoulder base portion. The shoulder tip portion is the tip-side portion that is directly press-fitted into the joining target, and the shoulder base portion is the base-end side portion that connects the driving device that generates a rotational force or the like and the shoulder tip portion.

[0006] Here, the shoulder tip, which is directly press-fitted into the object to be joined, is required to have high hardness from the viewpoint of wear resistance. On the other hand, the shoulder base does not require as high hardness as the shoulder tip, but in the aforementioned Patent Document 1, where the shoulder base and shoulder tip are integrated, it is reasonable to construct the shoulder base and shoulder tip from the same metal material. In this case, the entire shoulder, including the shoulder tip and shoulder base, is made of an expensive metal material (for example, cemented carbide) with sufficient hardness, which has the problem of easily increasing the unit cost of the shoulder.

[0007] Furthermore, due to wear and tear from continued use of the shoulder strap, cracks or other defects may occur at the tip of the shoulder strap. In this case, the tip of the shoulder strap needs to be replaced, but with the configuration described in Patent Document 1, the entire shoulder strap, including the tip and base, needs to be replaced, which presents the problem of high replacement costs.

[0008] This disclosure is made in view of the circumstances described above, and aims to provide a friction stir welding apparatus equipped with an inexpensive and easily maintainable shoulder, as well as a method for easily maintaining the said shoulder. [Means for solving the problem]

[0009] To solve the aforementioned problems, a friction stir welding apparatus according to one aspect of the present disclosure comprises a pin extending along an axis, a cylindrical shoulder coaxially arranged on the outer circumference of the pin, and a drive unit that moves the pin and the shoulder individually forward and backward along the axis while rotating them around the axis, wherein the shoulder includes a shoulder body having a tip portion that is press-fitted into the object to be joined, and a shoulder adapter having a fitting hole into which the base of the shoulder body is shrink-fitted and connecting the shoulder body and the drive unit.

[0010] A maintenance method for a friction stir welding apparatus relating to another aspect of this disclosure is a maintenance method for replacing the shoulder body in the friction stir welding apparatus described above, comprising: a first step of removing the shoulder body from the shoulder adapter by heating the shoulder adapter so that the fitting hole of the shoulder adapter expands in diameter; a second step of inserting the base of a new shoulder body into the fitting hole of the heated shoulder adapter; and a third step of fixing the new shoulder body to the shoulder adapter by cooling the shoulder adapter so that the fitting hole of the shoulder adapter shrinks in diameter. [Effects of the Invention]

[0011] This disclosure provides a friction stir welding apparatus equipped with an inexpensive and easily maintainable shoulder, as well as a method for easily maintaining the shoulder. [Brief explanation of the drawing]

[0012] [Figure 1] This is a front view showing the configuration of a friction stir welding apparatus according to the first embodiment of this disclosure. [Figure 2] This is a schematic diagram showing the system configuration of the friction stir welding apparatus. [Figure 3] This is a schematic diagram illustrating a joining method using the aforementioned friction stir welding apparatus and shoulder-first process. [Figure 4] This is a cross-sectional view showing an enlarged view of the rotating tool of the friction stir welding apparatus. [Figure 5] This is a flowchart showing the first step in the maintenance process for the aforementioned rotary tool. [Figure 6] This flowchart shows the second stage of the aforementioned maintenance work. [Figure 7] This flowchart shows the third stage of the aforementioned maintenance work. [Figure 8] This is a schematic diagram showing the configuration of a heating device for heating the aforementioned rotating tool. [Figure 9]It is a front view showing a situation where a pin adapter approaches a newly set pin body. [Figure 10] It is a cross-sectional view showing a situation where the upper part of the pin body is inserted into the pin adapter. [Figure 11] It is a schematic diagram showing the configuration of a cooling device for cooling the rotary tool. [Figure 12] It is a front view showing a situation where a shoulder adapter approaches a newly set shoulder body. [Figure 13] It is a cross-sectional view showing the situation immediately before the upper part of the shoulder body is inserted into the shoulder adapter. [Figure 14] It is a front view showing a situation where a clamp adapter approaches a newly set clamp body. [Figure 15] It is a cross-sectional view showing the situation immediately before the upper part of the clamp body is inserted into the clamp adapter. [Figure 16] It is a diagram corresponding to FIG. 4 for explaining a modification of the first embodiment. [Figure 17] It is a diagram corresponding to FIG. 4 for explaining another modification of the first embodiment. [Figure 18] It is a cross-sectional view of a rotary tool used in the second embodiment of the present invention. [Figure 19] It is a diagram corresponding to FIG. 13 for explaining the operation when replacing the shoulder body. [Embodiments for Carrying Out the Invention]

[0013] Hereinafter, embodiments of the present disclosure will be described in detail based on the drawings. The friction stir welding device according to the present disclosure can be applied to the manufacture of various joined bodies formed by overlapping two or more structural materials such as plates, frames, exterior materials, or columnar materials made of metal or resin and performing spot welding. The joined bodies to be manufactured can be used, for example, as constituent materials of structures such as aircraft, railway vehicles, or automobiles.

[0014] (1) First Embodiment [Friction Stir Welding Device] Figure 1 is a front view showing the configuration of a friction stir welding apparatus M according to the first embodiment of this disclosure, and Figure 2 is a schematic diagram showing the system configuration of the friction stir welding apparatus M. As shown in these figures, the friction stir welding apparatus M comprises a double-acting rotary tool 1, a base 2 supporting the rotary tool 1, a tool drive unit 3 (drive unit) that rotates and moves the rotary tool 1 up and down, a C-shaped frame 4 fixed to the base 2, a backing plate 5 fixed to the C-shaped frame 4, a heating device 6 for heating the rotary tool 1, a cooling device 7 for cooling the rotary tool 1, and a controller C that controls the operation of the tool drive unit 3, the heating device 6, and the cooling device 7. Note that Figures 1 and 2 are labeled "up" and "down," but this is for the convenience of explanation and is not intended to limit the actual orientation of the rotary tool 1.

[0015] The rotary tool 1 is positioned to protrude downward from the base 2 and is supported on the base 2 so as to be rotatable and vertically movable. The rotary tool 1 is positioned to face the backing plate 5 from above. Between the rotary tool 1 and the backing plate 5 is the object to be friction stir welding, i.e., the object to be joined. In this embodiment, the object to be joined is an overlapping portion 103 where plate-shaped first member 101 and second member 102 overlap in the thickness direction.

[0016] As shown in Figure 2, the rotary tool 1 comprises a pin 11, a shoulder 12, and a clamp 13.

[0017] The pin 11 is a rod-shaped (cylindrical) member, and is positioned so that its axis extends in the vertical direction. The pin 11 is capable of rotational movement, rotating around its axis as the axis of rotation R, and reciprocating movement, moving up and down along the axis of rotation R.

[0018] The shoulder 12 is positioned to cover the outer circumference of the pin 11. That is, the shoulder 12 is a cylindrical member with a hollow portion into which the pin 11 is inserted. The axis of the shoulder 12 is coaxial with the axis of the pin 11 (rotation axis R). The shoulder 12 is capable of rotational movement, rotating around the same rotation axis R as the pin 11, and forward and backward movement, moving up and down along the rotation axis R.

[0019] The rotary tool 1 of this embodiment is a double-acting tool in which the pin 11 and the shoulder 12 are independently movable in the axial direction. That is, the shoulder 12 and the pin 11 inserted therein can both rotate around the rotation axis R and move relative to each other in the vertical direction along the rotation axis R. In other words, the pin 11 and the shoulder 12 can not only move up and down simultaneously along the rotation axis R, but can also move independently, with one moving down and the other moving up.

[0020] The clamp 13 is positioned to cover the outer circumference of the shoulder 12. That is, the clamp 13 is a cylindrical member with a hollow section into which the shoulder 12 is inserted. The axis of the clamp 13 is also coaxial with the rotation axis R. The clamp 13 does not rotate around its axis, but it can move up and down along the rotation axis R. The clamp 13 serves to surround the outer circumference of the pin 11 or the shoulder 12 when they perform friction stirring. The enclosure by the clamp 13 prevents the friction-stirred material from scattering and allows the friction-stirred area to be finished smoothly.

[0021] A spring 14 is attached to the upper end of the clamp 13. The spring 14 biases the clamp 13 toward the object to be joined (overlapping portion 103), that is, downward. The clamp 13 is attached to the base 2 via the spring 14.

[0022] As shown in Figure 1, the base 2 is a housing that houses the tool drive unit 3 and supports the rotary tool 1 so that it can rotate and move up and down via the tool drive unit 3. The base 2 is fixed to a movable body 110 that can move relative to the object to be joined. The movable body 110 can be, for example, the end of an arm of a multi-joint robot. The movable body 110 can move the rotary tool 1 toward the overlapping portion 103 which is the object to be joined, or move the rotary tool 1 away from the overlapping portion 103.

[0023] The C-shaped frame 4 comprises a base portion 41 fixed to the side of the base 2, a tip portion 42 that supports the backing plate 5 from below, and a connecting portion 43 that connects the base portion 41 and the tip portion 42. The C-shaped frame 4 is formed in a roughly C-shape when viewed from the front, such that its tip portion 42 is positioned below the rotary tool 1.

[0024] The backing plate 5 is a plate-shaped member that is fixed to the tip 42 of the C-shaped frame 4 and positioned below the rotary tool 1. The backing plate 5 has a flat upper surface that contacts the lower surface of the overlapping portion 103 to be joined. In other words, the backing plate 5 is a support member that supports the overlapping portion 103 from below when joining by pressing the pin 11 or shoulder 12 of the rotary tool 1 into the overlapping portion 103. When joining by the rotary tool 1, the overlapping portion 103 is sandwiched and held between the clamp 13, which is biased downward by the spring 14, and the backing plate 5.

[0025] A load cell 45 is positioned between the tip 42 of the C-shaped frame 4 and the backing plate 5. The load cell 45 is a device that measures the load acting on the backing plate 5. The load measurement result from the load cell 45 is input as an electrical signal to the controller C (Figure 2).

[0026] As shown in Figure 2, the tool drive unit 3 comprises a rotary drive unit 31, a pin drive unit 32, a shoulder drive unit 33, and a clamp drive unit 34. The rotary drive unit 31 is a mechanism that rotates the pin 11 and the shoulder 12 around the rotation axis R. The pin drive unit 32 is a mechanism that moves the pin 11 forward and backward along the rotation axis R, causing the pin 11 to be pressed into and retracted from the overlapping portion 103. The shoulder drive unit 33 is a mechanism that moves the shoulder 12 forward and backward along the rotation axis R, causing the shoulder 12 to be pressed into and retracted from the overlapping portion 103. The clamp drive unit 34 is a mechanism that moves the clamp 13 forward and backward along the rotation axis R, performing an action to press the clamp 13 against the overlapping portion 103. At this time, the biasing force of the spring 14 acts. Each of the drive units 31 to 34 may include a motor and drive gears, etc.

[0027] The heating device 6 is a device that heats the rotary tool 1 from the outside during maintenance of the rotary tool 1. As shown in detail in Figure 8, the heating device 6 comprises an annular heater 61 arranged to surround the outer circumference of the rotary tool 1 and a power supply unit 62 that supplies power to the heater 61. The heater 61 can be, for example, a heater that heats the target by electromagnetic induction. In this case, the heater 61 heats the rotary tool 1 by electromagnetic induction based on the power supplied from the power supply unit 62. However, the heating method of the heater 61 is not limited to this, and any appropriate heating method can be applied, such as using hot air. Note that the maintenance of the rotary tool 1 referred to here refers to the work of replacing any of the pin body 111, shoulder body 121, and clamp body 131, which will be described later.

[0028] The cooling device 7 is a device that cools the rotary tool 1 from the outside during maintenance of the rotary tool 1. As shown in detail in Figure 11, the cooling device 7 comprises a plurality of nozzles 71 positioned to face the outer circumference of the rotary tool 1 from diagonally above, and an air source 72 that pressurizes and delivers air to each nozzle 71. The nozzles 71 cool the rotary tool 1 by blowing air supplied from the air source 72 onto the rotary tool 1.

[0029] Here, the heating device 6 and the cooling device 7 do not need to be permanently installed in the friction stir welding apparatus M, but may be provided temporarily during the maintenance of the rotary tool 1. For example, if a tool changer is used to perform the maintenance automatically, the friction stir welding apparatus M may be made to access the heating device 6 and the cooling device 7 provided in the tool changer.

[0030] Controller C consists of a microcomputer and the like, and controls the operation of the tool drive unit 3, heating device 6, and cooling device 7 by executing a predetermined control program. Specifically, Controller C controls the rotation drive unit 31 to cause the pin 11 and shoulder 12 to perform the required rotational movement. Controller C also controls the pin drive unit 32, shoulder drive unit 33, and clamp drive unit 34 to cause the pin 11, shoulder 12, and clamp 13 to perform the required forward and backward movement. Furthermore, Controller C controls the heating device 6 and cooling device 7 to perform heating and cooling operations on the rotating tool 1.

[0031] [Example of friction stir welding operation] The joining method using the friction stir welding apparatus M described above can be broadly classified into a shoulder-first process joining method and a pin-first process joining method. The shoulder-first process joining method involves pressing the shoulder 12 of the rotary tool 1 into the joining target (overlapping portion 103) before the pin 11, while the pin-first process joining method involves pressing the pin 11 of the rotary tool 1 into the joining target before the shoulder 12. Of these, the shoulder-first process is adopted in this embodiment.

[0032] Figure 3 is a schematic diagram showing the process of friction stir welding of the overlapping portion 103 of the first and second members 101 and 102, which are to be joined, using a shoulder-first process. The joining method using the shoulder-first process includes the following steps P11 to P14.

[0033] Step P11 is a preheating step for the overlapping portion 103. In this preheating step, the controller C rotates the pin 11 and shoulder 12 around their axis at a predetermined number of rotations while the tip (lower end) of the rotary tool 1 is in contact with the surface of the first member 101.

[0034] Step P12 is the press-fitting step of the shoulder 12. In this press-fitting step, the controller C lowers the shoulder 12 and presses it into the overlap 103, while retracting the pin 11 upward. This action stirs the material in the press-fitting area of ​​the shoulder 12. In addition, the overflow material OF that spills out from the overlap 103 due to the press-fitting is released into the hollow space within the shoulder 12 created by the retraction of the pin 11 (see arrow a1). Thus, in this embodiment, the pin 11 is moved upward relative to the shoulder 12 during friction stir welding.

[0035] Process P13 is a backfilling process for the overflow material OF. In this backfilling process, the controller C raises the shoulder 12 to move it away from the overlapping portion 103, while simultaneously lowering the pin 11. As the pin 11 is lowered, the overflow material OF that had been released into the hollow space is backfilled into the press-fitting region of the shoulder 12, as indicated by arrow a2.

[0036] Step P14 is a leveling step. In this leveling step, the controller C rotates the pin 11 and the shoulder 12 while returning their tips (lower ends) to the height of the upper surface of the first member 101. This shapes the upper surface of the overlapping portion 103 and smooths it to the extent that there are almost no irregularities.

[0037] Through the above steps P11 to P14, a joint JT with a smooth upper surface is formed, and the first member 101 and the second member 102 are point-joined at the overlapping portion 103.

[0038] [Detailed structure of the rotation tool] Figure 4 is a cross-sectional view showing an enlarged view of the rotary tool 1. As shown in Figures 4 and 2, the pin 11 includes a pin body 111 and a pin adapter 112 that connects the pin body 111 to the tool drive unit 3. The pin body 111 is a rod-shaped (cylindrical) member that extends vertically along the rotation axis R. The pin adapter 112 is a rod-shaped member that is slightly larger than the pin body 111 and is positioned above the pin body 111 so as to extend coaxially with the pin body 111. A portion of the tip side (lower side) of the pin adapter 112 functions as a retaining portion 112a that holds a portion of the base side of the pin body 111, i.e., the upper part 111b. That is, the retaining portion 112a of the pin adapter 112 has a fitting hole H1 formed in it, which is a cylindrical recess with an open bottom surface. The pin body 111 is fixedly held by the pin adapter 112 by fitting its upper part 111b into the fitting hole H1.

[0039] Specifically, the pin body 111 is joined to the pin adapter 112 by shrink-fitting. As is well known, shrink-fitting is a joining method in which a shaft is fitted into a hole that has been expanded by heating. That is, the inner diameter of the fitting hole H1 of the pin adapter 112 is slightly smaller than the outer diameter of the upper part 111b of the pin body 111 at room temperature. During shrink-fitting, the pin adapter 112 is heated and the inner diameter of the fitting hole H1 is expanded, and the upper part 111b of the pin body 111 is inserted into this expanded fitting hole H1. Subsequently, as the pin adapter 112 cools and its temperature decreases, the fitting hole H1 shrinks in diameter and the pin body 111 is firmly joined to the pin adapter 112.

[0040] The pin adapter 112 is connected to the rotary drive unit 31 and the pin drive unit 32 (Figure 2) of the tool drive unit 3. When the pin adapter 112 is rotated and moved forward and backward by the rotary drive unit 31 and the pin drive unit 32, the pin body 111 also rotates and moves forward and backward together with the pin adapter 112. In other words, the pin adapter 112 holds the pin body 111 so that the driving force of the tool drive unit 3 can be transmitted to the pin body 111. When joining the overlapping portion 103, the pin adapter 112 presses the pin body 111 downward while rotating it, thereby pressing the lower part 111a of the pin body 111 into the overlapping portion 103.

[0041] The outer diameter of the pin body 111 is constant in the vertical direction (axial direction). That is, the outer diameter of the pin body 111 is the same at both the upper part 111b that is fitted into the pin adapter 112 and the lower part 111a that is press-fitted into the overlapping part 103. In other words, the pin body 111 is formed in a straight rod shape such that the outer diameter of the base part (upper part 111b) that is fitted into the pin adapter 112 and the outer diameter of the tip part (lower part 111a) that is press-fitted into the overlapping part 103 are the same.

[0042] The shoulder 12 includes a shoulder body 121 and a shoulder adapter 122 that connects the shoulder body 121 to the tool drive unit 3. The shoulder body 121 is a cylindrical member that extends vertically along the rotation axis R. The shoulder body 121 has a hollow portion into which the pin body 111 is inserted and is positioned to cover the outer circumference of the pin body 111. The shoulder adapter 122 is a cylindrical member that is slightly larger than the shoulder body 121, and is positioned above the shoulder body 121, extending coaxially with the shoulder body 121 and covering the outer circumference of the pin adapter 112. A portion of the tip side (lower side) of the shoulder adapter 122 functions as a holding portion 122a that holds a portion of the base side of the shoulder body 121, i.e., the upper part 121b. That is, the holding portion 122a of the shoulder adapter 122 has a fitting hole H2 formed in it, which is a through hole with a circular cross-section. The shoulder strap body 121 is fixedly held by the shoulder adapter 122 by fitting its upper part 121b into the fitting hole H2.

[0043] Specifically, the shoulder body 121 is joined to the shoulder adapter 122 by shrink-fitting, similar to the pin body 111 described above. That is, the inner diameter of the fitting hole H2 of the shoulder adapter 122 is slightly smaller than the outer diameter of the upper part 121b of the shoulder body 121 at room temperature. During shrink-fitting, the shoulder adapter 122 is heated, and the inner diameter of the fitting hole H2 is expanded, into which the upper part 121b of the shoulder body 121 is inserted. Subsequently, as the shoulder adapter 122 cools and its temperature decreases, the fitting hole H2 shrinks, and the shoulder body 121 is firmly joined to the shoulder adapter 122.

[0044] The shoulder adapter 122 is connected to the rotary drive unit 31 and the shoulder drive unit 33 (Figure 2) of the tool drive unit 3. When the shoulder adapter 122 is rotated and moved forward and backward by the rotary drive unit 31 and the shoulder drive unit 33, the shoulder body 121 also rotates and moves forward and backward together with the shoulder adapter 122. In other words, the shoulder adapter 122 holds the shoulder body 121 so that the driving force of the tool drive unit 3 can be transmitted to the shoulder body 121. When joining the overlapping portion 103, the shoulder adapter 122 presses the shoulder body 121 downward while rotating it, thereby pressing the lower part 121a of the shoulder body 121 into the overlapping portion 103.

[0045] The outer diameter of the shoulder strap body 121 is constant in the vertical direction (axial direction). That is, the outer diameter of the shoulder strap body 121 is the same at both the upper part 121b that fits into the shoulder adapter 122 and the lower part 121a that is press-fitted into the overlapping part 103. In other words, the shoulder strap body 121 is formed in a straight cylindrical shape such that the outer diameter of the base part (upper part 121b) that fits into the shoulder adapter 122 and the outer diameter of the tip part (lower part 121a) that is press-fitted into the overlapping part 103 are the same.

[0046] A chamfer F1 is formed on the upper part 121b of the shoulder body 121. The chamfer F1 is a tapered shape formed by cutting the inner circumference of the upper end, which is near the end face of the upper part 121b of the shoulder body 121, in a tapered shape. Due to this chamfer F1, the upper end of the shoulder body 121 is formed such that the inner diameter of its hollow part increases as it approaches the end face (upper end).

[0047] The clamp 13 includes a clamp body 131 and a clamp adapter 132 that connects the clamp body 131 to the tool drive unit 3. The clamp body 131 is a cylindrical member that extends vertically along the rotation axis R. The clamp body 131 has a hollow portion into which the shoulder body 121 is inserted and is positioned to cover the outer circumference of the shoulder body 121. The clamp adapter 132 is a cylindrical member that is slightly larger than the clamp body 131 and is positioned above the clamp body 131, extending coaxially with the clamp body 131 and covering the outer circumference of the shoulder adapter 122. A portion of the tip side (lower side) of the clamp adapter 132 functions as a holding portion 132a that holds a portion of the base side of the clamp body 131, i.e., the upper part 131b. That is, the holding portion 132a of the clamp adapter 132 has a fitting hole H3 formed in it, which is a through hole with a circular cross-section. The clamp body 131 is fixedly held by the clamp adapter 132 by fitting its upper part 131b into the fitting hole H3.

[0048] Specifically, the clamp body 131 is joined to the clamp adapter 132 by shrink-fitting, similar to the pin body 111 and shoulder body 121 described above. That is, the inner diameter of the fitting hole H3 of the clamp adapter 132 is slightly smaller than the outer diameter of the upper part 131b of the clamp body 131 at room temperature. During shrink-fitting, the clamp adapter 132 is heated, and the inner diameter of the fitting hole H3 is expanded, into which the upper part 131b of the clamp body 131 is inserted. Subsequently, as the clamp adapter 132 cools and its temperature decreases, the fitting hole H3 shrinks, and the clamp body 131 is firmly joined to the clamp adapter 132.

[0049] The clamp adapter 132 is connected to the clamp drive unit 34 (Figure 2) of the tool drive unit 3 via a spring 14. When the clamp adapter 132 is moved forward and backward by the clamp drive unit 34, the clamp body 131 also moves forward and backward together with the clamp adapter 132. In other words, the clamp adapter 132 holds the clamp body 131 so that the driving force of the clamp drive unit 34 can be transmitted to the clamp body 131 via the spring 14. When joining the overlapping portion 103, the clamp adapter 132, receiving the biasing force of the spring 14, presses the clamp body 131 against the overlapping portion 103.

[0050] The outer diameter of the clamp body 131 is constant in the vertical direction (axial direction). That is, the outer diameter of the clamp body 131 is the same at both the upper part 131b that fits into the clamp adapter 132 and the lower part 131a that abuts against the overlapping part 103. In other words, the clamp body 131 is formed in a straight cylindrical shape such that the outer diameter of the base part (upper part 131b) that fits into the clamp adapter 132 and the outer diameter of the tip part (lower part 131a) that abuts against the overlapping part 103 are the same.

[0051] A chamfer F2 is formed on the upper part 131b of the clamp body 131. The chamfer F2 is a tapered shape formed by cutting the inner circumference of the upper end, which is near the end face of the upper part 131b of the clamp body 131, in a tapered shape. Due to this chamfer F2, the upper end of the clamp body 131 is formed such that the inner diameter of its hollow portion increases as it approaches the end face (upper end).

[0052] As described above, the pin 11, shoulder 12, and clamp 13 are all composed of a combination of a body and an adapter joined by shrink-fitting. Specifically, the pin 11 is composed of a pin body 111 that is shrink-fitted into a pin adapter 112, the shoulder 12 is composed of a shoulder body 121 that is shrink-fitted into a shoulder adapter 122, and the clamp 13 is composed of a clamp body 131 that is shrink-fitted into a clamp adapter 132. In this embodiment, the bodies and adapters of the pin 11, shoulder 12, and clamp 13 are composed of a combination of metal materials with different hardness and thermal expansion coefficients.

[0053] Specifically, the pin adapter 112, shoulder adapter 122, and clamp adapter 132 are all made of tool steel. On the other hand, the pin body 111, shoulder body 121, and clamp body 131 are all made of cemented carbide. Cemented carbide is an alloy that has higher hardness than tool steel. The reason why cemented carbide is used as the material for the pin body 111, shoulder body 121, and clamp body 131 is that each of these components is press-fitted into or in contact with the overlapping portion 103, and therefore high wear resistance is required.

[0054] Furthermore, due to its properties, cemented carbide has a lower coefficient of thermal expansion than tool steel. Therefore, the coefficient of thermal expansion of the cemented carbide pin body 111 is lower than that of the tool steel pin adapter 112. Similarly, the coefficient of thermal expansion of the shoulder body 121 is lower than that of the shoulder adapter 122, and the coefficient of thermal expansion of the clamp body 131 is lower than that of the clamp adapter 132.

[0055] [Maintenance method for rotary tools] The pin body 111, shoulder body 121, and clamp body 131 described above are parts that are press-fitted or in contact with the overlapping portion 103, and therefore are expected to deteriorate with continued use. For example, the end faces of the lower parts (111a, 121a, 131a) of the pin body 111, shoulder body 121, and clamp body 131 may wear excessively or cracks may develop on these end faces. Therefore, as part of the maintenance of the rotary tool 1, it is desirable to periodically replace the pin body 111, shoulder body 121, and clamp body 131. In this embodiment, the friction stir welding apparatus M performs bonding by a shoulder-first process in which the shoulder body 121 is press-fitted into the overlapping portion 103 first, so it is considered that the shoulder body 121 is particularly prone to deterioration among the pin body 111, shoulder body 121, and clamp body 131. Therefore, maintenance of the rotary tool 1 in this embodiment only requires replacing the shoulder body 121, and it is not necessary to replace the pin body 111 and the clamp body 131. However, this description will focus on maintenance procedures assuming that all three components—the pin body 111, the shoulder body 121, and the clamp body 131—are replaced.

[0056] Figures 5 to 7 are flowcharts illustrating the procedure for maintenance work on the rotary tool 1. In this embodiment, the maintenance work based on the flowchart is performed autonomously by the controller C according to a predetermined program, and is started when a predetermined signal to command the start of the work is input by an operator.

[0057] As described above, when a signal to start work is input and the control shown in Figure 5 starts, the controller C removes the pin body 111, the shoulder body 121, and the clamp body 131 (step S1). This removal is performed by releasing the shrink-fit of each component.

[0058] In other words, in step S1, the controller C uses the heating device 6 to heat the pin adapter 112, the shoulder adapter 122, and the clamp adapter 132, causing each adapter to expand due to heat. Specifically, as shown in Figure 8, the controller C controls the power supply unit 62 so that power is supplied to the heater 61 of the heating device 6, and heats the pin adapter 112, the shoulder adapter 122, and the clamp adapter 132 via the heater 61. The heating by the heating device 6 raises the temperature not only of the pin adapter 112, the shoulder adapter 122, and the clamp adapter 132, but also of the pin body 111, the shoulder body 121, and the clamp body 131 fitted to the adapters. However, as already explained, in this embodiment, the materials of each component are selected such that the thermal expansion coefficient of the pin body 111, the shoulder body 121, and the clamp body 131 is smaller than the thermal expansion coefficient of the pin adapter 112, the shoulder adapter 122, and the clamp adapter 132. Therefore, the adapters expand more significantly when heated by the heating device 6. In other words, the pin adapter 112 expands more than the pin body 111, the shoulder adapter 122 expands more than the shoulder body 121, and the clamp adapter 132 expands more than the clamp body 131. The heating by the heating device 6 described above creates these differences in thermal expansion, which releases the shrink-fit. As a result of releasing the shrink-fit, the pin body 111, shoulder body 121, and clamp body 131 can be removed from the pin adapter 112, shoulder adapter 122, and clamp adapter 132, respectively. For example, when removing the shoulder body 121, the shoulder body 121 is held by a holding mechanism such as a chuck (not shown), and the shoulder drive unit 33 (Figure 2) is driven to raise the shoulder adapter 122. This allows the upper part 121b of the shoulder body 121 to be pulled out from the fitting hole H2 of the shoulder adapter 122, thereby removing the shoulder member 121. The pin body 111 and the clamp body 131 can also be removed from the pin adapter 112 and the clamp adapter 132 in the same manner.

[0059] Next, the controller C determines whether or not a new pin body 111 has been set (step S2). That is, once the removal of the pin body 111 etc. in step S1 is complete, a new pin body 111 is set on the backing plate 5, as shown in Figure 9. The setting position of this pin body 111 is a predetermined position such that the pin body 111 is located on the same axis as the pin adapter 112. The controller C recognizes that the setting of the new pin body 111 is complete when a signal indicating completion is input.

[0060] The setting of the new pin body 111 described above may be done manually by an operator, but it can also be done automatically using a predetermined tool changer. In this case, the movement of the mobile body 110 (Figure 1) allows the friction stir welding apparatus M to access the tool changer, and in that state, the new pin body 111 is automatically set on the backing plate 5 of the friction stir welding apparatus M. This automatic setting capability is also available when setting the shoulder body 121 and clamp body 131 (S11, S21), which will be described later.

[0061] If step S2 is determined to be YES and the completion of setting the new pin body 111 is confirmed, the controller C heats the pin adapter 112 using the heating device 6 (step S3). This heating is achieved by supplying power from the power supply unit 62 to the heater 61, as in step S1. The heating by the heater 61 causes the pin adapter 112 to expand due to heat, thereby increasing the inner diameter of its fitting hole H1.

[0062] Next, controller C lowers the pin adapter 112 (step S4). That is, as shown by the white arrow in Figure 9, controller C drives the pin drive unit 32 (Figure 2) to lower the pin adapter 112 so that the pin adapter 112 approaches the pin body 111 set on the backing plate 5. When the pin adapter 112 is lowered, the pin drive unit 32, shoulder drive unit 33, and clamp drive unit 34 are driven in coordination so that the shoulder adapter 122 and clamp adapter 132 also lower in parallel with the pin adapter 112.

[0063] Next, the controller C determines whether the pressing force of the pin adapter 112 is less than or equal to a predetermined threshold Fx (step S5). The pressing force of the pin adapter 112 here refers to the downward pressing force applied from the pin adapter 112 to the pin body 111 as the pin adapter 112 descends. The controller C determines the pressing force based on the output from the load cell 45 below the backing plate 5 and compares the determined pressing force with the threshold Fx.

[0064] If step S5 determines NO and it is confirmed that the pressing force of the pin adapter 112 exceeds the threshold Fx, the controller C performs a predetermined error handling process, such as notifying the worker of the abnormality (step S9).

[0065] If the pin adapter 112 is properly heated by the heating device 6 and the concentricity between the pin body 111 and the pin adapter 112 is good, then, as shown in Figure 10, the upper part 111b of the pin body 111 should be properly inserted into the fitting hole H1 of the pin adapter 112 as the pin adapter 112 descends. In this case, the resistance force acting on the pin adapter 112 in response to this insertion will not be very large. Conversely, if the pin adapter 112 is not sufficiently heated due to a malfunction of the heating device 6 or the like, or if the concentricity between the pin body 111 and the pin adapter 112 is significantly misaligned, then insertion of the pin body 111 into the fitting hole H1 will become difficult, and an excessive resistance force will act on the pin adapter 112. If the pushing force of the pin adapter 112 exceeds the threshold Fx, it means that the insertion of the pin body 111 is being hindered due to the latter circumstances. Therefore, in step S9, the controller C performs error processing to inform the worker that an abnormal situation has occurred in which the insertion is being hindered.

[0066] On the other hand, if step S5 determines YES and it is confirmed that the pushing force of the pin adapter 112 is less than or equal to the threshold Fx, that is, if no error has occurred that prevents the insertion of the pin body 111, the controller C determines whether the pin adapter 112 has descended to a predetermined position (step S6). For example, the controller C determines the vertical position of the pin adapter 112 based on the output from the encoder (position detection unit) provided on the motor of the pin drive unit 32, and makes the determination based on the determined position.

[0067] If step S6 determines NO and it is confirmed that the pin adapter 112 has not yet reached the specified position, the controller C returns to step S5 and continues the process of lowering the pin adapter 112 while determining the pressing force.

[0068] On the other hand, if step S6 determines that YES and it is confirmed that the pin adapter 112 has reached the predetermined position, the controller C determines that the upper part 111b of the pin body 111 has been inserted into the mating hole H1 by the predetermined insertion amount and stops the descent of the pin adapter 112 (step S7).

[0069] Next, the controller C cools the pin adapter 112 using the cooling device 7 (step S8). That is, as shown in Figure 11, the controller C supplies air to the air source 72 of the cooling device 7, and blows the supplied air from the air source 72 onto the rotary tool 1 through the nozzle 71. The air blown from the nozzle 71 cools the pin adapter 112 by air cooling. At the time of step S8, only the pin body 111 is attached to the pin adapter 112, and the shoulder body 121 and clamp body 131 are not attached to the shoulder adapter 122 and clamp adapter 132. However, for convenience, Figure 11 shows the shoulder body 121 and clamp body 131 together with the pin body 111.

[0070] The cooling of the pin adapter 112 in step S8 releases the thermal expansion of the pin adapter 112, causing the diameter of the fitting hole H1 to shrink. As a result, the upper part 111b of the pin body 111 is tightened within the fitting hole H1, and the pin body 111 is firmly coupled to the pin adapter 112. In other words, the shrink-fitting of the pin body 111 to the pin adapter 112 is completed.

[0071] Once the replacement of the pin body 111 is completed through the process described above, the flow proceeds to the steps shown in Figure 6, and the replacement of the shoulder body 121 begins. When the control shown in Figure 6 starts, the controller C determines whether or not the new shoulder body 121 has been set (step S11). That is, after the replacement of the pin body 111 shown in Figure 5 is completed, the new shoulder body 121 is set on the backing plate 5 as shown in Figure 12. The setting position of this shoulder body 121 is a predetermined position such that the shoulder body 121 is located on the same axis as the shoulder adapter 122. The controller C recognizes that the setting of the new shoulder body 121 is complete when a signal indicating completion is input.

[0072] If step S11 is determined to be YES and the completion of setting the new shoulder body 121 is confirmed, the controller C heats the shoulder adapter 122 using the heating device 6 (step S12). This heating is achieved by supplying power from the power supply unit 62 to the heater 61, as in step S3 described above. The heating by the heater 61 causes the shoulder adapter 122 to expand thermally, enlarging the inner diameter of its fitting hole H2.

[0073] Next, controller C lowers the shoulder adapter 122 (step S13). That is, as shown by the white arrow in Figure 12, controller C drives the shoulder drive unit 33 (Figure 2) to lower the shoulder adapter 122 so that the shoulder adapter 122 approaches the shoulder body 121 set on the backing plate 5. When the shoulder adapter 122 is lowered, the pin drive unit 32, shoulder drive unit 33, and clamp drive unit 34 are driven in coordination so that the pin adapter 112 and clamp adapter 132 also lower in parallel with the shoulder adapter 122.

[0074] Next, the controller C determines whether the pressing force of the shoulder adapter 122, that is, the downward pressing force applied from the shoulder adapter 122 to the shoulder body 121, is less than or equal to a predetermined threshold Fy (step S14). This determination is made based on the output from the load cell 45, as in step S5 described above.

[0075] If step S14 determines NO and it is confirmed that the pressing force of the shoulder adapter 122 exceeds the threshold Fy, the controller C performs a predetermined error processing, such as notifying the worker of the abnormality (step S18). The pressing force exceeding the threshold Fy means that the insertion of the shoulder body 121 into the fitting hole H2 is being hindered due to insufficient heating, misalignment of concentricity, etc. The processing in step S18 is to notify the worker that such an obstruction has occurred.

[0076] As previously explained, in this embodiment, a chamfer F1 is formed on the periphery of the upper end opening of the shoulder body 121. When the shoulder adapter 122 descends, the guide function of this chamfer F1 makes it easier to ensure concentricity between the shoulder body 121 and the shoulder adapter 122. This has the effect of reducing the possibility of error processing occurring in step S18. That is, as the shoulder adapter 122 descends together with the pin adapter 112, the lower part 111a of the previously replaced pin body 111 approaches the upper end of the shoulder body 121 set on the backing plate 5. At this time, the chamfer F1 at the upper end of the shoulder body 121 functions as a guide for the insertion of the pin body 111, so that, as shown in Figure 13, the pin body 111 is inserted into the shoulder body 121 with a high probability, the axis of the pin body 111 and the axis of the shoulder body 121 are aligned, and consequently the concentricity between the shoulder body 121 and the shoulder adapter 122 is ensured. Therefore, as long as the heating of the shoulder adapter 122 is normal, the upper part 121b of the shoulder body 121 is inserted into the fitting hole H2 of the shoulder adapter 122 with a high probability. This reduces the probability that the insertion of the shoulder body 121 is hindered and increases the probability that the judgment in step S14 is YES.

[0077] If step S14 determines YES and it is confirmed that the pushing force of the shoulder adapter 122 is less than or equal to the threshold Fy, that is, if no error has occurred that prevents the insertion of the shoulder body 121, the controller C determines whether the shoulder adapter 122 has descended to a predetermined position (step S15). For example, the controller C determines the vertical position of the shoulder adapter 122 based on the output from the encoder (position detection unit) provided on the motor of the shoulder drive unit 33, and makes the determination based on the determined position.

[0078] If step S15 determines NO and it is confirmed that the shoulder adapter 122 has not yet reached the specified position, the controller C returns to step S14 and continues the process of lowering the shoulder adapter 122 while determining the pressing force.

[0079] On the other hand, if step S15 determines that YES and it is confirmed that the shoulder adapter 122 has reached the predetermined position, the controller C determines that the upper part 121b of the shoulder body 121 has been inserted into the fitting hole H2 by the predetermined insertion amount and stops the descent of the shoulder adapter 122 (step S16).

[0080] Next, the controller C cools the shoulder adapter 122 using the cooling device 7 (step S17). Cooling here is achieved by supplying air from the air source 72 to the nozzle 71, as in step S8 described above. The air blown out from the nozzle 71 cools the shoulder adapter 122 and reduces the inner diameter of its fitting hole H2. As a result, the upper part 121b of the shoulder body 121 is tightened within the fitting hole H2, and the shrink-fit of the shoulder body 121 is completed.

[0081] Once the replacement of the shoulder body 121 is completed through the process described above, the flow proceeds to the steps shown in Figure 7, and the replacement of the clamp body 131 begins. When the control shown in Figure 7 starts, the controller C determines whether or not the new clamp body 131 has been set (step S21). That is, after the replacement of the shoulder body 121 as shown in Figure 6, the new clamp body 131 is set on the backing plate 5 as shown in Figure 14. The setting position of this clamp body 131 is a predetermined position such that the clamp body 131 is located on the same axis as the clamp adapter 132. The controller C recognizes that the setting of the new clamp body 131 is complete when a signal indicating completion is input.

[0082] If step S21 is determined to be YES and the completion of setting the new clamp body 131 is confirmed, the controller C heats the clamp adapter 132 using the heating device 6 (step S22). This heating is achieved by supplying power from the power supply unit 62 to the heater 61, as in steps S3 and S12 described above. The heating by the heater 61 causes the clamp adapter 132 to expand thermally, enlarging the inner diameter of its fitting hole H3.

[0083] Next, controller C lowers the clamp adapter 132 (step S23). That is, as shown by the white arrow in Figure 14, controller C drives the clamp drive unit 34 (Figure 2) to lower the clamp adapter 132 so that the clamp adapter 132 approaches the clamp body 131 set on the backing plate 5. When the clamp adapter 132 is lowered, the pin drive unit 32, shoulder drive unit 33, and clamp drive unit 34 are driven in coordination so that the pin adapter 112 and shoulder adapter 122 also lower in parallel with the clamp adapter 132.

[0084] Next, the controller C determines whether the pressing force of the clamp adapter 132, that is, the downward pressing force applied from the clamp adapter 132 to the clamp body 131, is less than or equal to a predetermined threshold Fz (step S24). This determination is made based on the output from the load cell 45, as in steps S5 and S14 described above.

[0085] If step S24 determines NO and it is confirmed that the pressing force of the clamp adapter 132 exceeds the threshold Fz, the controller C performs a predetermined error handling process, such as notifying the worker of the abnormality (step S28). The pressing force exceeding the threshold Fz means that the insertion of the clamp body 131 into the fitting hole H3 is being hindered due to insufficient heating, misalignment of concentricity, etc. The process in step S28 is to notify the worker that such an obstruction has occurred.

[0086] However, in this embodiment, the possibility of error processing in step S28 occurring is low. The reason is the same as in step S18 described above. That is, in this embodiment, a chamfer F2 is formed on the periphery of the upper end opening of the clamp body 131. Due to the guiding function of this chamfer F2, as shown in Figure 15, the shoulder body 121 that was replaced earlier is inserted into the inside of the clamp body 131 with a high probability, making it easier to ensure concentricity between the clamp body 131 and the clamp adapter 132. Therefore, as long as the heating of the clamp adapter 132 is normal, the upper part 131b of the clamp body 131 is inserted into the fitting hole H3 of the clamp adapter 132 with a high probability. This reduces the probability that the insertion of the clamp body 131 is hindered and increases the probability that the judgment in step S24 will be YES.

[0087] If step S24 determines that the result is YES and it is confirmed that the pressing force of the clamp adapter 132 is less than or equal to the threshold Fz, that is, if no error has occurred that would prevent the insertion of the clamp body 131, the controller C determines whether the clamp adapter 132 has descended to a predetermined position (step S25). For example, the controller C determines the vertical position of the clamp adapter 132 based on the output from the encoder (position detection unit) provided on the motor of the clamp drive unit 34, and makes the determination based on the determined position.

[0088] If step S25 determines NO and it is confirmed that the clamp adapter 132 has not yet reached the specified position, the controller C returns to step S24 and continues the process of lowering the clamp adapter 132 while determining the pressing force.

[0089] On the other hand, if step S25 determines that YES and it is confirmed that the clamp adapter 132 has reached the specified position, the controller C determines that the upper part 131b of the clamp body 131 has been inserted into the fitting hole H3 by the predetermined insertion amount and stops the descent of the clamp adapter 132 (step S26).

[0090] Next, the controller C cools the clamp adapter 132 using the cooling device 7 (step S27). Cooling here is achieved by supplying air from the air source 72 to the nozzle 71, as in steps S8 and S17 described above. The air blown out from the nozzle 71 cools the clamp adapter 132 and reduces the inner diameter of its fitting hole H3. As a result, the upper part 131b of the clamp body 131 is tightened within the fitting hole H3, and the shrink-fitting of the clamp body 131 is completed.

[0091] In the above-described maintenance method for the rotary tool 1, step S1, which includes the process of removing the shoulder body 121 from the shoulder adapter 122 by heating the shoulder adapter 122 to cause thermal expansion, corresponds to the first step in this disclosure; steps S3 to S7, in which the upper part 121b of the new shoulder body 121 is inserted into the fitting hole H2 of the heated shoulder adapter 122, correspond to the second step in this disclosure; and step S8, in which the shoulder body 121 is fixed to the shoulder adapter 122 by cooling the shoulder adapter 122 to cause contraction, corresponds to the third step in this disclosure.

[0092] [Effects and Effects] As described above, in this embodiment, the pin body 111, shoulder body 121, and clamp body 131 are joined to the pin adapter 112, shoulder adapter 122, and clamp adapter 132, respectively, by shrink-fitting. This reduces component costs and improves maintainability, thereby enhancing the marketability of the friction stir welding apparatus M.

[0093] For example, in this embodiment, where the shoulder body 121 is joined to the shoulder adapter 122 by shrink-fitting, the shoulder body 121 and the shoulder adapter 122 can be made of appropriate materials according to their respective required characteristics. Specifically, the shoulder body 121, which is directly press-fitted into the joining target (overlapping portion 103), can be made of a cemented carbide with excellent wear resistance, while the shoulder adapter 122, which holds the shoulder body 121, can be made of steel (tool steel in this embodiment), which has lower hardness and is less expensive than cemented carbide. As a result, the total component cost of the shoulder 12 can be reduced compared to, for example, the case where the shoulder body 121 and the shoulder adapter 122 are integrally made of cemented carbide.

[0094] Furthermore, even if there are concerns about deterioration of the shoulder strap body 121 due to continued use, the shoulder adapter 122 can be reused while only the shoulder strap body 121 is replaced, which has the advantage of improving maintainability. In other words, since the shoulder strap body 121 is shrink-fitted to the shoulder adapter 122, the shrink-fit can be released and the shoulder strap body 121 can be removed from the shoulder adapter 122 by heating the shoulder adapter 122 to cause thermal expansion. Then, the new shoulder strap body 121 can be inserted into the fitting hole H2 of the thermally expanded shoulder adapter 122, and then the shoulder adapter 122 can be cooled to contract, thereby fixing the new shoulder strap body 121 to the shoulder adapter 122. Thus, in this embodiment, the shoulder adapter 122 can be reused while only the shoulder strap body 121 is replaced, which reduces the cost of parts replacement and improves maintainability.

[0095] Furthermore, in this embodiment, where cemented carbide is used as the material for the shoulder body 121 and tool steel is used as the material for the shoulder adapter 122, the thermal expansion coefficient of the shoulder adapter 122 is greater than that of the shoulder body 121. Therefore, when the shoulder adapter 122 is heated during replacement of the shoulder body 121, the shoulder adapter 122 will naturally expand more than the shoulder body 121. As a result, the shrink-fit is released and the shoulder body 121 becomes removable, allowing for easy and accurate replacement of the shoulder body 121.

[0096] The same effects can be obtained for the pin body 111 and the clamp body 131. That is, materials suitable for the required characteristics can be selected for the pin body 111 and the pin adapter 112, and during maintenance, only the pin body 111 can be replaced while reusing the pin adapter 112. Similarly, materials suitable for the required characteristics can be selected for the clamp body 131 and the clamp adapter 132, and during maintenance, only the clamp body 131 can be replaced while reusing the clamp adapter 132. As a result, both parts costs and maintenance costs can be reduced.

[0097] Furthermore, in this embodiment, the pin body 111 and the shoulder body 121 are formed in a straight shape such that their outer diameter is constant in the vertical direction (axial direction). This has the advantage of facilitating the replacement of the pin body 111 and the shoulder body 121.

[0098] For example, if the outer diameter of the upper part 121b of the shoulder body 121 is larger than the outer diameter of the lower part 121a, the upper part 121b is more likely to interfere with the clamp adapter 132 when replacing the shoulder body 121, so it may be necessary to remove the clamp adapter 132 in advance before replacing the shoulder body 121. Similarly, if the outer diameter of the upper part 111b of the pin body 111 is larger than the outer diameter of the lower part 111a, it may be necessary to remove the shoulder adapter 122 in advance before replacing the pin body 111. In contrast, in this embodiment in which the pin body 111 and shoulder body 121 are straight, the pin body 111 and shoulder body 121 can be replaced respectively with the shoulder adapter 122 and clamp adapter 132 attached, reducing the man-hours required for such replacement and facilitating maintenance work.

[0099] In Figures 5 to 15, examples were shown of replacing the pin body 111, shoulder body 121, and clamp body 131. However, since the shoulder body 121 is the most prone to deterioration, it is also possible to replace only the shoulder body 121 and reuse the pin body 111 and clamp body 131. According to the configuration of this embodiment, even when only the shoulder body 121 is replaced in this way, the work efficiency can be significantly improved.

[0100] In other words, in this embodiment, the pin body 111, the shoulder body 121 outside of it, and the clamp body 131 further outside are all formed in a straight shape. Therefore, as shown in Figure 15, throughout the entire axial range, the relationship holds that the outer diameter R3 of the shoulder body 121 is smaller than the inner diameter R4 of the clamp body 131, and the outer diameter R1 of the pin body 111 is smaller than the inner diameter R2 of the shoulder body 121. This means that the shoulder body 121 can be removed from the shoulder adapter 122 independently while the clamp body 131 and pin body 111 remain connected to the clamp adapter 132. Thus, in this embodiment, the clamp body 131 and pin body 111 can be reused, and only the shoulder body 121, which is prone to deterioration, can be replaced independently, thereby effectively improving the ease of replacing the shoulder body 121 and, consequently, the maintainability of the rotary tool 1.

[0101] [Differentiation] In the first embodiment described above, the pin body 111, the shoulder body 121, and the clamp body 131 are all formed in a straight shape having a constant outer diameter in the vertical direction (axial direction). However, each member does not necessarily have to be straight, and may have a shape in which the outer diameter changes along the way. For example, it may have a stepped shape in which the outer diameter of the upper part is relatively smaller. An example of adopting such a stepped shape is shown in Figure 16. That is, in the modified example shown in Figure 16, the pin body 211 includes an upper part 211b (base) that is fitted into the fitting hole H11 of the pin adapter 212 and a lower part 211a (tip) that is press-fitted into the overlapping part 103, and is formed such that the outer diameter of the upper part 211b is smaller than the outer diameter of the lower part 211a. Similarly, the shoulder body 221 includes an upper part 221b (base) that fits into the fitting hole H12 of the shoulder adapter 222 and a lower part 221a (tip) that is press-fitted into the overlapping part 103, and is formed such that the outer diameter of the upper part 221b is smaller than the outer diameter of the lower part 221a. The clamp body 231 includes an upper part 231b (base) that fits into the fitting hole H13 of the clamp adapter 232 and a lower part 231a (tip) that is press-fitted into the overlapping part 103, and is formed such that the outer diameter of the upper part 231b is smaller than the outer diameter of the lower part 231a. Even in this configuration, the pin body 211, shoulder body 221, and clamp body 231 can be easily replaced while each component can be appropriately joined to the mating adapter by shrink-fitting. In Figure 16, an example was shown in which a stepped shape with a smaller upper diameter is applied to all of the pin body 111, shoulder body 121, and clamp body 131. However, such a stepped shape may be applied to only some of the components. For example, the stepped shape may not be applied to the clamp body 131, but only to the pin body 111 and shoulder body 121.

[0102] Furthermore, contrary to the modified example in Figure 16, a stepped shape with a larger upper diameter may be adopted. As an example, Figure 17 shows an example in which a stepped shape with a larger upper diameter is applied to the clamp body 331. That is, in the modified example shown in Figure 17, the clamp body 331 includes an upper part 331b (base) that fits into the fitting hole H23 of the clamp adapter 332, a lower part 331a (tip) that abuts against the overlapping part 103, and an intermediate part 331c located between the upper part 331b and the lower part 331a. The inner and outer diameters of the upper part 331b are larger than the inner and outer diameters of the lower part 331a. The intermediate part 331c is formed to smoothly connect the upper part 331b and the lower part 331a, with its diameter decreasing towards the bottom. On the other hand, the shape of the shoulder body 321 is different from that of the clamp body 331. In other words, the shoulder body 321 includes an upper part 321b (base) that fits into the fitting hole H22 of the shoulder adapter 322 and a lower part 321a (tip) that is press-fitted into the overlapping part 103, and is formed such that the outer diameter of the upper part 321b is smaller than the outer diameter of the lower part 321a. In addition, the inner diameter of the shoulder body 321 is constant along the axial direction. The shape of the pin body 311 is not particularly limited, but here the pin body 311 is formed such that its outer diameter is constant in the range below the pin adapter 312.

[0103] As described above, in the modified example shown in Figure 17, the trend of change in the inner and outer diameters along the axial direction differs between the shoulder body 321 and the clamp body 331. However, in this modified example, since the maximum outer diameter RA of the shoulder body 321 is smaller than the minimum inner diameter RB of the clamp body 331, the same effect as in the first embodiment can be obtained, which is that it is not necessary to remove the clamp body 331 when replacing the shoulder body 321 alone. That is, in order to position the shoulder body 321 inside the clamp body 331, the outer diameter of the lower part 321a of the shoulder body 321 is necessarily smaller than the inner diameter of the lower part 331a of the clamp body 331. Here, if we let RA be the outer diameter of the lower part 321a of the shoulder body 321, then RA can be rephrased as the maximum value of the outer diameter of the shoulder body 321, that is, the maximum outer diameter of the shoulder body 321. Furthermore, if the inner diameter of the lower part 331a of the clamp body 331 is denoted as RB, then RB can be rephrased as the minimum inner diameter of the clamp body 331, or the minimum inner diameter of the clamp body 331. From this, in the modified example shown in Figure 17, the relationship holds that the maximum outer diameter RA of the shoulder body 321 is smaller than the minimum inner diameter RB of the clamp body 331. This means that the shoulder body 321 can be attached to and detached from the shoulder adapter 322 while the clamp body 331 remains connected to the clamp adapter 332. Thus, according to the modified example shown in Figure 17, even though the upper part of the clamp body 331 has an enlarged shape, it becomes unnecessary to remove the clamp body 331 in advance when replacing the shoulder body 321. Therefore, there is an advantage in that the ease of replacing the shoulder body 321 can be improved while ensuring sufficient mounting rigidity of the clamp body 331. Note that the form in Figure 17 may be further modified so that the shoulder body 331 has a straight shape similar to the shoulder body 131 of the first embodiment.

[0104] In the first embodiment described above, the pin body 111, the shoulder body 121, and the clamp body 131 were each joined to the mating adapter by shrink-fitting. However, shrink-fitting is only required for the shoulder body, which is most susceptible to deterioration, and shrink-fitting of the pin body and clamp body is not essential.

[0105] In the first embodiment described above, the shoulder adapter 122 is made of tool steel, while the shoulder body 121 is made of cemented carbide. However, the materials of the two can be any combination such that the thermal expansion coefficient of the shoulder adapter 122 is greater than that of the shoulder body 121, and the hardness of the shoulder body 121 is greater than that of the shoulder adapter 122. The specific materials can be changed as appropriate. For example, the material of the shoulder adapter 122 may be a structural alloy steel such as SCM435, a structural carbon steel such as S45C, or stainless steel. The material of the shoulder body 121 may be a CBN sintered body (PCBN), a PCD (polycrystalline diamond sintered body), or ceramics, or a high melting point alloy such as a Co-based alloy, a Ni-based alloy, or an Ir-based alloy. The same applies to the material combinations of the pin adapter 112 and the pin body 111, and the material combinations of the clamp adapter 132 and the clamp body 131.

[0106] In the first embodiment described above, a load cell 45 positioned below the backing plate 5 was used as a means for measuring the pressing force (axial load) during tool replacement. However, the pressing force may also be measured based on the operating current of the motor in the tool drive unit 3, for example.

[0107] (2) Second Embodiment In the first embodiment and its modifications described above, the dimensional relationship was set so that only the shoulder body can be replaced while the clamp body remains attached. However, such a dimensional relationship is not mandatory. Below, an example of a dimensional relationship set on the premise that the clamp body is removed when replacing the shoulder body will be described as the second embodiment.

[0108] Figure 18 is a cross-sectional view showing the structure of the rotary tool 1 of a friction stir welding apparatus M according to a second embodiment of the present invention. The rotary tool 1 shown in this figure comprises a pin 11 including a pin adapter 412 and a pin body 411 that is shrink-fitted thereto, a shoulder 12 including a shoulder adapter 422 and a shoulder body 421 that is shrink-fitted thereto, and a clamp 13 including a clamp adapter 432 and a shoulder body 431 that is shrink-fitted thereto. Unlike the first embodiment, the shoulder body 421 and the clamp body 431 have a stepped shape with a larger diameter at the top.

[0109] In other words, the shoulder body 421 includes an upper part 421b (base) that fits into the fitting hole H32 of the shoulder adapter 422, a lower part 421a (tip) that is press-fitted into the overlapping part 103, and an intermediate part 421c located between the upper part 421b and the lower part 421a. The inner and outer diameters of the upper part 421b are larger than the inner and outer diameters of the lower part 421a. The intermediate part 421c is formed to smoothly connect the upper part 421b and the lower part 421a, with its diameter decreasing towards the bottom.

[0110] The inner circumferential surface of the intermediate portion 421c of the shoulder body 421 is a tapered surface in which the inner diameter decreases towards the bottom. In other words, the inner circumferential surface of the shoulder body 421 has a tapered portion T1 in which the inner diameter decreases towards the tip.

[0111] The clamp body 431 includes an upper part 431b (base) that fits into the fitting hole H33 of the clamp adapter 432, a lower part 431a (tip) that abuts against the overlapping part 103, and an intermediate part 431c located between the upper part 431b and the lower part 431a. The inner and outer diameters of the upper part 431b are larger than those of the lower part 431a. The intermediate part 431c is formed to smoothly connect the upper part 431b and the lower part 431a, with its diameter decreasing towards the bottom.

[0112] In the second embodiment, the outer diameter of the upper part 421b of the shoulder body 421, i.e., the maximum outer diameter RC of the shoulder body 421, is larger than the inner diameter of the lower part 431a of the clamp body 431, i.e., the minimum inner diameter RD of the clamp body 431. Therefore, unlike the first embodiment, it is necessary to remove the clamp body 431 beforehand when replacing the shoulder body 421. On the other hand, in the second embodiment, since the upper parts of the shoulder body 421 and the clamp body 431 are enlarged, there is an advantage in that sufficient mounting rigidity of the shoulder body 421 and the clamp body 431 can be ensured.

[0113] Furthermore, in the second embodiment, the inner diameter of the upper part 421b of the shoulder body 421 is larger than the inner diameter of the lower part 421a, and the inner circumferential surface of the intermediate part 421c between them is tapered T1. As described below, this has the advantage of improving the positioning accuracy when replacing the shoulder body 421.

[0114] Figure 19 shows the situation when inserting the pin body 411 into the shoulder body 421 for the installation of a new shoulder body 421, after the shoulder body 421 has been removed from the shoulder adapter 422. As shown in this figure, in the second embodiment, the inner diameter of the upper part 421b of the shoulder body 421 is relatively enlarged, so the lower part 411a of the pin body 411 can be easily inserted into the upper part 421b. Furthermore, as the insertion amount (downward movement) of the pin body 411 increases, the lower part 411a of the pin body 411 slides against the tapered portion T1 on the inner circumferential surface of the shoulder body 421, and a force acts to correct the insertion position of the pin body 411 with respect to the shoulder body 421, that is, the relative position of the pin body 411 on a plane perpendicular to the insertion direction (up and down direction) into the shoulder body 421. This corrective force corrects the position of the shoulder body 421 on the backing plate 5, ensuring that the axis of the pin body 411 and the axis of the shoulder body 421 coincide. To ensure that such position correction is performed accurately, a jig that actively allows for misalignment of the shoulder body 421 on the backing plate 5 may be used. For example, a jig that supports the shoulder body 421 so that it can slide on a plane perpendicular to the insertion direction. Using such a jig, the position of the shoulder body 421 is autonomously adjusted so that the axis of the pin body 411 and the axis of the shoulder body 421 coincide. In this way, in the second embodiment, the concentricity between the pin body 411 and the shoulder body 421 can be autonomously ensured, thereby improving the positioning accuracy when replacing the shoulder body 421.

[0115] Here, as a backup in case the autonomous position adjustment function described above does not work as expected, or if the insertion of the pin body 411 is hindered due to an abnormal tilt of the shoulder body 421, it is desirable for the controller C to adjust the insertion position of the pin member 411 while measuring the axial load acting on the pin body 411. That is, the controller C identifies the axial load applied to the pin body 411 when the pin body 411 is inserted into the shoulder body 421, for example, based on the output from the load cell 45 (Figure 2), and adjusts the insertion position of the pin body 411 so that the identified axial load does not exceed a predetermined value. This ensures that the pin body 411 is accurately positioned relative to the shoulder body 421, and that the concentricity between the two is well maintained while avoiding excessive axial load.

[0116] [summary] The embodiments and their modifications described above include the following disclosures.

[0117] A friction stir welding apparatus according to one aspect of the present disclosure comprises a pin extending along an axis, a cylindrical shoulder coaxially arranged on the outer circumference of the pin, and a drive unit that moves the pin and the shoulder individually forward and backward along the axis while rotating them around the axis. The shoulder includes a shoulder body having a tip portion that is press-fitted into the object to be joined, and a shoulder adapter having a fitting hole into which the base of the shoulder body is shrink-fitted and connecting the shoulder body and the drive unit.

[0118] According to this disclosure, since the shoulder body is joined to the shoulder adapter by shrink-fitting, the shoulder body and shoulder adapter can be made of appropriate materials according to their respective required characteristics. Specifically, the shoulder body, which is directly press-fitted into the object to be joined, can be made of a highly hard alloy with excellent wear resistance, while the shoulder adapter that holds the shoulder body can be made of steel or other material that is less hard and less expensive than the shoulder body. As a result, the total component cost of the shoulder can be reduced compared to, for example, a case where the shoulder body and shoulder adapter are integrally made of a highly hard alloy.

[0119] Furthermore, even if there are concerns about deterioration of the shoulder strap body due to continued use, the shoulder adapter can be reused while only the shoulder strap body is replaced, which has the advantage of improving maintainability. In other words, since the shoulder strap body is shrink-fitted into the shoulder adapter, the shrink-fit can be released by heating the shoulder adapter to cause thermal expansion, allowing the shoulder strap body to be removed from the shoulder adapter. Then, a new shoulder strap body can be inserted into the fitting hole of the thermally expanded shoulder adapter, and after that, the shoulder adapter can be cooled to contract, thereby fixing the new shoulder strap body to the shoulder adapter. Thus, according to this disclosure, since only the shoulder strap body can be replaced while reusing the shoulder adapter, the cost of parts replacement can be reduced and maintainability can be improved.

[0120] Preferably, the thermal expansion coefficient of the shoulder adapter is greater than that of the shoulder body.

[0121] In this embodiment, when the shoulder adapter is heated during the replacement of the shoulder strap body, the shoulder adapter will naturally expand more than the shoulder strap body due to thermal expansion. This releases the shrink-fit and allows the shoulder strap body to be removed, thus enabling easy and accurate replacement of the shoulder strap body.

[0122] As a specific example, the shoulder body may be made of cemented carbide, and the shoulder adapter may be made of tool steel.

[0123] In this embodiment, the difference in thermal expansion coefficients described above can be achieved while ensuring sufficient wear resistance of the shoulder body.

[0124] Preferably, the shoulder body is formed such that the outer diameter of the base portion, which is shrink-fitted into the shoulder adapter, is less than or equal to the outer diameter of the tip portion, which is press-fitted into the object to be joined.

[0125] In this embodiment, the replacement of the shoulder strap body can be made easier.

[0126] The shoulder body may be formed such that the inner and outer diameters of the base portion, which is shrink-fitted into the shoulder adapter, are larger than the inner and outer diameters of the tip portion, which is press-fitted into the object to be joined. In this case, it is preferable that the inner circumferential surface of the shoulder body is provided with a tapered portion, the inner diameter of which decreases towards the tip.

[0127] In this way, by relatively increasing the diameter of the base of the shoulder strap body, sufficient mounting rigidity of the shoulder strap body can be ensured. Furthermore, when inserting a pin into the shoulder strap body for mounting a new shoulder strap body after removing the old one from the shoulder adapter, the insertion of the pin can be made easier. Moreover, due to the action of the tapered portion provided on the inner circumferential surface of the shoulder strap body, the insertion position of the pin relative to the shoulder strap body is corrected, resulting in good concentricity between the pin and the shoulder strap body, thus improving the positioning accuracy when replacing the shoulder strap body.

[0128] Preferably, the friction stir welding apparatus further comprises a cylindrical clamp coaxially arranged on the outer circumference of the shoulder. The clamp includes a clamp body that abuts against the objects to be joined and a clamp adapter to which the base of the clamp body is coupled. The shoulder body is formed such that its maximum outer diameter is less than the minimum inner diameter of the clamp body.

[0129] In this embodiment, the shoulder body can be attached to and detached from the shoulder adapter while the clamp body remains connected to the clamp adapter. This allows the shoulder body to be easily replaced independently, improving the maintainability of the rotary tool.

[0130] Preferably, the pin includes a pin body having a tip portion that is press-fitted into the object to be joined, and a pin adapter having a fitting hole into which the base portion of the pin body is shrink-fitted, and which connects the pin body and the drive unit.

[0131] In this embodiment, materials suitable for the required characteristics can be selected for the pin body and pin adapter, and only the pin body can be replaced during maintenance. This reduces both parts costs and maintenance costs.

[0132] A maintenance method relating to another aspect of this disclosure is a maintenance method for replacing the shoulder body in the friction stir welding apparatus described above, comprising: a first step of removing the shoulder body from the shoulder adapter by heating the shoulder adapter so that the fitting hole of the shoulder adapter expands in diameter; a second step of inserting the base of a new shoulder body into the fitting hole of the heated shoulder adapter; and a third step of fixing the new shoulder body to the shoulder adapter by cooling the shoulder adapter so that the fitting hole of the shoulder adapter shrinks in diameter.

[0133] This method allows for easy and accurate replacement of the shoulder strap.

[0134] Preferably, in the second step, the shoulder adapter is brought axially closer to the new shoulder body, which is positioned opposite the shoulder adapter, together with the pin, so that the tip of the pin is inserted into the new shoulder body, and the base of the shoulder body is inserted into the fitting hole of the shoulder adapter.

[0135] In this way, the shoulder strap body and the shoulder strap adapter can be aligned properly, while ensuring good concentricity between them.

[0136] Furthermore, a tapered portion may be provided on the inner circumferential surface of the shoulder body, where the inner diameter decreases towards the tip. In this case, it is preferable in the second step to insert the pin into the shoulder body while measuring the axial load applied to the pin.

[0137] In this way, excessive axial load during pin insertion can be avoided while ensuring good concentricity between the shoulder body and the pin, thereby improving positioning accuracy when replacing the shoulder body. [Explanation of symbols]

[0138] M Friction Stir Welding Apparatus 3. Tool drive unit (drive unit) 11 pins 12 shoulders 13 Clamp 103 Overlapping section (to be joined) 111 Pin Body 111a Lower part (tip of the pin body) 111b Top (base of the pin body) 112-pin adapter 121 Shoulder bag 121a Lower part (tip of the shoulder strap) 121b Upper part (base of the shoulder strap) 122 Shoulder Adapter 131 Clamp body 132 Clamp Adapter H1 (pin adapter) mating hole H2 (Shoulder adapter) fitting hole T1 Tapered section

Claims

1. A pin extending along the axis, A cylindrical shoulder is coaxially arranged on the outer circumference of the aforementioned pin, The system includes a drive unit that rotates the pin and the shoulder around the axis and moves them individually forward and backward along the axis, The aforementioned shoulder includes a shoulder body having a tip portion that is press-fitted into the object to be joined, and a shoulder adapter having a fitting hole into which the base portion of the shoulder body is shrink-fitted, and which connects the shoulder body and the drive unit, in a friction stir welding apparatus.

2. In the friction stir welding apparatus according to claim 1, A friction stir welding apparatus wherein the thermal expansion coefficient of the shoulder adapter is greater than that of the shoulder body.

3. In the friction stir welding apparatus according to claim 2, A friction stir welding apparatus in which the shoulder body is made of cemented carbide and the shoulder adapter is made of tool steel.

4. In the friction stir welding apparatus according to any one of claims 1 to 3, A friction stir welding apparatus wherein the shoulder body is formed such that the outer diameter of the base portion, which is shrink-fitted into the shoulder adapter, is less than or equal to the outer diameter of the tip portion, which is press-fitted into the object to be joined.

5. In the friction stir welding apparatus according to any one of claims 1 to 3, The shoulder body is formed such that the inner and outer diameters of the base portion, which is shrink-fitted into the shoulder adapter, are larger than the inner and outer diameters of the tip portion, which is press-fitted into the object to be joined. A friction stir welding apparatus, wherein the inner circumferential surface of the shoulder body is provided with a tapered portion whose inner diameter decreases towards the tip.

6. In the friction stir welding apparatus according to any one of claims 1 to 3, The shoulder further comprises a cylindrical clamp coaxially positioned on its outer circumference, The clamp includes a clamp body that contacts the object to be joined and a clamp adapter to which the base of the clamp body is connected. A friction stir welding apparatus in which the shoulder body is formed such that its maximum outer diameter is less than the minimum inner diameter of the clamp body.

7. In the friction stir welding apparatus according to any one of claims 1 to 3, The friction stir welding apparatus includes a pin body having a tip portion that is press-fitted into the objects to be joined, and a pin adapter having a fitting hole into which the base portion of the pin body is shrink-fitted, and which connects the pin body and the drive unit.

8. A maintenance method for replacing the shoulder body in a friction stir welding apparatus according to any one of claims 1 to 3, The first step involves heating the shoulder adapter so that the fitting hole of the shoulder adapter expands in diameter, thereby removing the shoulder body from the shoulder adapter. The second step is to insert the base of a new shoulder body into the fitting hole of the heated shoulder adapter, A method for maintaining a friction stir welding apparatus, comprising a third step of fixing a new shoulder body to the shoulder adapter by cooling the shoulder adapter so that the fitting hole of the shoulder adapter shrinks in diameter.

9. In the maintenance method for a friction stir welding apparatus described in claim 8, A method for maintaining a friction stir welding apparatus, wherein in the second step, the shoulder adapter is brought axially closer to a new shoulder body positioned opposite the shoulder adapter, together with the pin, thereby inserting the tip of the pin into the new shoulder body and inserting the base of the shoulder body into the fitting hole of the shoulder adapter.

10. In the maintenance method for a friction stir welding apparatus described in claim 9, The inner circumferential surface of the shoulder body is provided with a tapered portion in which the inner diameter decreases towards the tip. A method for maintaining a friction stir welding apparatus, the second step being to insert the pin into the shoulder body while measuring the axial load applied to the pin.

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