Patent ID: 12202066

MODES FOR CARRYING OUT THE DISCLOSURE

Hereinafter, desirable embodiments of the present disclosure will be described with reference to the drawings. Note that, below, the same reference characters are assigned to the same or corresponding elements throughout the drawings to omit redundant explanation. Further, throughout the drawings, components which are necessary to explain the present disclosure are selectively illustrated, and illustration of other components may be omitted. Moreover, the present disclosure is not limited to the following embodiments.

Embodiment 1

Below, one example of a friction stir spot welding apparatus according to Embodiment 1 is described in detail with reference to the drawings.

[Configuration of Friction Stir Spot Welding Apparatus]

FIG.1is a schematic diagram illustrating an outline configuration of the friction stir spot welding apparatus according to Embodiment 1. Note that, inFIG.1, an up-and-down direction in this drawing is expressed as an up-and-down direction of the friction stir spot welding apparatus.

As illustrated inFIG.1, a friction stir spot welding apparatus50according to Embodiment 1 includes a pin member11, a shoulder member12, a tool fixator52, a linear actuator53, a clamp member13, a backing support part55, a backing member56, and a rotary actuator57.

The pin member11, the shoulder member12, the tool fixator52, the linear actuator53, the clamp member13, and the rotary actuator57are provided to an upper end of the backing support part55which is comprised of a C-shaped gun (C-shaped frame). The backing member56is provided to a lower end of the backing support part55. The pin member11, the shoulder member12, the clamp member13, and the backing member56are attached to the backing support part55so that the pin member11, the shoulder member12, and the clamp member13are located at a position opposing to the backing member56. Note that an object60to be joined (to-be-joined object60) is disposed between the pin member11, the shoulder member12, and the clamp member13, and the backing member56.

The pin member11, the shoulder member12, and the clamp member13are fixed to the tool fixator52which is comprised of a rotary tool fixator521and a clamp fixator522. In detail, the pin member11and the shoulder member12are fixed to the rotary tool fixator521, and the clamp member13is fixed to the clamp fixator522via a clamp actuator41. Further, the rotary tool fixator521is supported by the clamp fixator522via the rotary actuator57. Note that the clamp actuator41is comprised of a spring.

Further, the pin member11, the shoulder member12, and the clamp member13are linearly moved in the up-and-down direction by the linear actuator53which is comprised of a pin actuator531and a shoulder actuator532.

The pin member11is formed in a solid cylindrical shape, and although not illustrated in detail inFIG.1, it is supported by the rotary tool fixator521. Moreover, the pin member11is configured to be rotatable by the rotary actuator57on an axis Xr (rotation axis) which is in agreement with the axial center of the pin member11, and to be linearly movable by the pin actuator531in an arrow P1direction (inFIG.1, the up-and-down direction), i.e., the axis Xr direction.

Note that the pin actuator531may be comprised of a linear actuator, for example. The linear actuator may be comprised of a servomotor and a rack-and-pinion mechanism, or a servomotor and a ball-screw mechanism, or an air cylinder, for example.

The shoulder member12is formed in a hollow cylindrical shape, and is supported by the rotary tool fixator521. The pin member11is inserted in the hollow shoulder member12. In other words, the shoulder member12is disposed so as to surround an outer circumferential surface of the pin member11.

Moreover, the shoulder member12is configured to be rotatable by the rotary actuator57on the axis Xr same as the pin member11, and to be linearly movable by the shoulder actuator532in an arrow P2direction, i.e., the axis Xr direction.

Note that the shoulder actuator532may be comprised of a linear actuator, for example. The linear actuator may be comprised of a servomotor and a rack-and-pinion mechanism, or a servomotor and a ball-screw mechanism, or an air cylinder, for example.

Thus, in this embodiment, both the pin member11and the shoulder member12(rotary tool) are supported by the same rotary tool fixator521, and are rotated by the rotary actuator57integrally on the axis Xr. Further, the pin member11and the shoulder member12are configured to be linearly movable by the pin actuator531and the shoulder actuator532, respectively, in the axis Xr direction.

Note that, although in Embodiment 1 the pin member11is linearly movable alone and is also linearly movable in association with the linear movement of the shoulder member12, the pin member11and the shoulder member12may be configured to be linearly movable independently.

Similarly to the shoulder member12, the clamp member13is formed in a hollow cylindrical shape, and it is provided so that its axial center is in agreement with the axis Xr. The shoulder member12is inserted into the hollow clamp member13.

That is, the cylindrical shoulder member12is disposed so as to surround the outer circumferential surface of the pin member11, and the cylindrical clamp member13is disposed so as to surround an outer circumferential surface of the shoulder member12. In other words, the clamp member13, the shoulder member12, and the pin member11have a coaxial telescopic structure.

Further, the clamp member13is configured so as to press the to-be-joined object60from one of the surfaces (upper surface). As described above, in Embodiment 1, the clamp member13is supported by the clamp fixator522via the clamp actuator41. The clamp actuator41is configured to bias the clamp member13toward the backing member56. Further, the clamp member13(including the clamp actuator41and the clamp fixator522) is configured to be linearly movable by the shoulder actuator532in an arrow P3direction (the same direction as the arrow P1and the arrow P2).

Note that, although in Embodiment 1 the clamp actuator41is comprised of the spring, it is not limited to this configuration. The clamp actuator41may be any configuration as long as it biases or applies a pressing force to the clamp member13, and, for example, a mechanism using gas pressure, oil pressure, a servomotor, etc. may also be conveniently used as the clamp actuator41.

The pin member11, the shoulder member12, and the clamp member13are provided with a tip-end surface11a, a tip-end surface12a, and a tip-end surface13a, respectively. Further, the tip-end surface11aof the pin member11and the tip-end surface12aof the shoulder member12are configured to be in agreement with each other, when seen horizontally.

Moreover, the pin member11, the shoulder member12, and the clamp member13are linearly moved by the linear actuator53so that the tip-end surface11a, the tip-end surface12a, and the tip-end surface13aeach contact the upper surface of the to-be-joined object60(a joining part of the to-be-joined object60) and press the to-be-joined object60.

A tip-end part120of the shoulder member12is formed in a tapered shape. Here, the shape of the tip-end part120of the shoulder member12is described in detail with reference toFIG.2.

FIG.2is a schematic diagram in which a substantial part of the friction stir spot welding apparatus illustrated inFIG.1is enlarged.

As illustrated inFIG.2, in Embodiment 1, the tip-end part120is formed so that an outer circumferential surface12band an inner circumferential surface12cof the shoulder member12incline to the axis Xr. In other words, the tip-end part120is formed so that its cross-sectional shape in the axis Xr direction is substantially V-shaped (substantially U-shaped), when seen horizontally.

Further, the tip-end part120is a part (area) from the tip-end surface12aof the shoulder member12to a given height h. In terms of stamping (transferring) the shape of the tip-end part120onto the surface of the to-be-joined object60, the height h may be 0.05 mm or more, or may be 5% or more of the thickness of a first member61, for example. Further, in terms of suppressing damage to the tip-end part120of the shoulder member12, the height h may be 0.5 mm or less, or may be 50% or less of the thickness of the first member61, for example.

Note that the tip-end part120may be formed so that its radial cross-sectional area becomes smaller as it goes toward the tip end. Further, as for the tip-end part120, the shapes of the outer circumferential surface12band the inner circumferential surface12cof the tip-end part120may be any kind of shapes, as long as the area of a tip end12d(the tip-end surface12a) of the tip-end part120is smaller than the radial cross-sectional area of a base end12eof the tip-end part120.

As illustrated inFIG.1, in Embodiment 1, the backing member56is configured to support the back surface (lower surface) of the to-be-joined object60of a flat plate shape so as to contact the back surface by a flat surface (support surface56a). The configuration of the backing member56is not limited in particular, as long as it can appropriately support the to-be-joined object60to carry out friction stir joining or welding. For example, as for the backing member56, a plurality of shapes may be prepared separately, and it may be configured to be removable from the backing support part55and replaceable according to the type of the to-be-joined object60.

The to-be-joined object60has two plate-like members, the first member61and a second member62. The first member61is disposed so as to oppose to the pin member11and the shoulder member12, and is made of material with a melting point lower than the second member62.

Note that, as for the to-be-joined object60, a third member may be disposed between the first member61and the second member62. The third member may be made of metal (for example, aluminum, aluminum alloy, or magnesium alloy), or may be sealant material, for example. The sealant material may be sealing material or adhesive. As the sealant material, polysulfide-based synthetic rubber, natural rubber, synthetic rubber, such as silicone rubber and fluororubber, and synthetic resin, such as tetrafluoroethylene rubber resin, for example.

For the first member61, at least one material among metals (for example, aluminum, aluminum alloy, and magnesium alloy), thermoplastics (for example, polyamide), and fiber-reinforced plastics (for example, carbon-fiber-reinforced plastics) may be used. As the aluminum alloy, various kinds of aluminum alloys may be used, and, for example, Al—Mg—Si based alloy (A6061) may be used, or Al—Si—Mg based alloy (AC4C) may be used.

Further, for the second member62, metal (for example, steel or titanium) may be used. As the steel, various kinds of steels may be used, and soft steel or high-strength steel may be used. Further, on the surface of steel, an oxide film may be formed, or a deposit or plating layer (for example, galvanization) may be formed. A steel plate where galvanization is formed may be a hot-dip galvanized steel plate (GI steel plate), an alloyed hot-dip galvanized steel plate (GA steel plate), a Galvalume® steel plate, or an aluminum-silicon-coated hot-stamped steel plate. Further, the thickness of the deposit may be 2 micrometers to 50 micrometers.

Note that, although in Embodiment 1 the to-be-joined object60is comprised of the plate-like first member61and the plate-like second member62, it is not limited to this configuration. The shape of the to-be-joined object60(the first member61and the second member62) is arbitrary, and, for example, it may be a rectangular parallelepiped shape, or may be formed circularly. Similarly, the shape of the third member is also arbitrary, and, for example, it may be a plate shape, or may be a rectangular parallelepiped shape, or may be formed circularly.

Further, in Embodiment 1, the concrete configurations of the pin member11, the shoulder member12, the tool fixator52, the linear actuator53, the clamp member13, the backing support part55, and the rotary actuator57are not limited to the configurations described above, but they may conveniently use widely-known configurations in the friction stir welding field. For example, the pin actuator531and the shoulder actuator532may be comprised of a motor and gear mechanism etc. which is known in the friction stir welding field.

Although in Embodiment 1 the backing support part55is comprised of the C-shaped gun, it is not limited to this configuration. The backing support part55may be configured in any way, as long as it can support the pin member11, the shoulder member12, and the clamp member13so as to be linearly movable, and can support the backing member56at the position which opposes to the pin member11, the shoulder member12, and the clamp member13.

Further, although in Embodiment 1 the clamp member13is provided, it is not limited to this configuration, but the clamp member13may not be provided. In this case, for example, the clamp member13may be configured to be detachable from and attachable to the backing support part55, as needed.

Further, in the friction stir spot welding apparatus50according to Embodiment 1, it is disposed at a robot device for friction stir spot welding (not illustrated). In detail, the backing support part55is attached to a tip end of an arm of the robot device.

Thus, the backing support part55may also be considered to be included in the robot device for friction stir spot welding. The concrete configuration of the robot device for friction stir spot welding, including the backing support part55and the arm, is not limited in particular, but it may conveniently use a configuration known in the friction stir welding field, such as articulated robots.

Note that the friction stir spot welding apparatus50(including the backing support part55) is not limited to the case where it is applied to the robot device for friction stir spot welding, and, for example, it can also be suitably applied to known machining apparatuses, such as NC machine tools, large-sized C-frames, and auto riveters.

Further, as for the friction stir spot welding apparatus50according to Embodiment 1, two or more pairs of robots may be configured so that the backing member56opposes to a part of the friction stir spot welding apparatus50other than the backing member56. Moreover, as long as the friction stir spot welding apparatus50can stably perform the friction stir spot welding to the to-be-joined object60, the to-be-joined object60may be of a hand-held type, or the robot may be used as a positioner for the to-be-joined

[Control Configuration of Friction Stir Spot Welding Apparatus]

Next, a control configuration of the friction stir spot welding apparatus50according to Embodiment 1 is described concretely with reference toFIG.3.

FIG.3is a block diagram schematically illustrating the control configuration of the friction stir spot welding apparatus illustrated inFIG.1.

As illustrated inFIG.3, the friction stir spot welding apparatus50includes a controller51, a memory31, a user interface32, and a position detector33.

The controller51is comprised of a microprocessor, a CPU, etc., and is configured to control each member (each apparatus) which constitutes the friction stir spot welding apparatus50. In detail, the controller51controls the pin actuator531and the shoulder actuator532which constitute the linear actuator53, and the rotary actuator57, by reading and executing software, such as a basic program, stored in the memory.

Therefore, switching between advancing and retreating of the pin member11and the shoulder member12, a control of the tip-end positions of the pin member11and the shoulder member12during the linear movement (advancing and retreating), a moving speed, a moving direction, etc. are controllable. Further, a pressing force of the pin member11, the shoulder member12, and the clamp member13for pressing the to-be-joined object60is controllable. In addition, a rotational speed of the pin member11and the shoulder member12is controllable.

Note that the controller51may be a sole controller51which carries out a centralized control, or may be comprised of a plurality of controllers51which collaboratively carry out a distributed control. Further, the controller51may be comprised of a microcomputer, or may be comprised of an MPU, a PLC (Programmable Logic Controller), a logical circuit, etc.

The memory31stores the basic program and various data possible so that the basic program and various data can be read out, and it is comprised of a known storage device, such as a memory and a hard disk drive. The memory31does not need to be a single memory, but it may be comprised of a plurality of storage devices (for example, a random-access memory and a hard disk drive). If the controller51etc. is comprised of the microcomputer, at least a part of the memory31may be configured as an internal memory of the microcomputer, or it may be configured as an independent memory.

Note that it is needless to say that data may be stored in the memory31, the data may be readable by devices other than the controller51, and it may be writable by the controller51etc.

The user interface32enables an input of various parameters related to the control of the friction stir spot welding, or other data etc. to the controller51, and is comprised of a known input device, such as a keyboard, a touch panel, and a button switch group. In Embodiment 1, at least welding conditions of the to-be-joined object60(for example, data such as the thickness and the material of the to-be-joined object60) can be inputted via the user interface32.

The position detector33is configured to detect positional information on the tip end (the tip-end surface12a) of the shoulder member12, and output the detected positional information to the controller51. As the position detector33, a displacement sensor, an LVDT, an encoder, etc. may be used, for example.

[Operation (Operating Method) of Friction Stir Spot Welding Apparatus]

Next, operation of the friction stir spot welding apparatus50according to Embodiment 1 is described concretely with reference toFIGS.4,5A, and5B. Note that, inFIGS.5A and5B, one example in which the first member61and the second member62are used as the to-be-joined object60and these members are coupled by spot welding in a stacked state is illustrated.

FIG.4is a flowchart illustrating one example of operation of the friction stir spot welding apparatus according to Embodiment 1.FIGS.5A and5Bare process charts schematically illustrating one example of each process of the friction stir spot welding by the friction stir spot welding apparatus illustrated inFIG.1.

Note that, inFIGS.5A and5B, a part of the friction stir spot welding apparatus is omitted, an arrow r indicates a rotating direction of the pin member11and the shoulder member12, and a block arrow F indicates a direction of a force applied to each of the first member61and the second member62. Further, although a force is also applied from the backing member56to each of the first member61and the second member62, it is not illustrated inFIGS.5A and5Bfor convenience of the explanation. Further, in order to clarify the distinction from the pin member11and the clamp member13, the shoulder member12is hatched in a shading manner.

First, a worker (operator) places the to-be-joined object60on the support surface56aof the backing member56. Then, the worker operates the user interface32to input welding execution of the to-be-joined object60to the controller51. Note that a robot may place the to-be-joined object60on the support surface56aof the backing member56.

Then, as illustrated inFIG.4, the controller51drives the rotary actuator57so that the pin member11and the shoulder member12rotate at a given first rotational speed set beforehand (for example, 200 to 3000 rpm) (Step S101; see PROCESS (1) inFIG.5A).

Next, the controller51drives the linear actuator53(the shoulder actuator532), while the pin member11and the shoulder member12being rotating, so that the pin member11, the shoulder member12, and the clamp member13are brought closer to the to-be-joined object60and the tip-end surface11aof the pin member11, the tip-end surface12aof the shoulder member12, and the tip-end surface13aof the clamp member13(not illustrated inFIGS.5A and5B) contact a surface60cof the to-be-joined object60(a joining part Wa of the to-be-joined object60) (Step S102; see PROCESS (2) inFIG.5A).

At this time, the controller51controls the linear actuator53(the shoulder actuator532) so that the pin member11, the shoulder member12, and the clamp member13press the to-be-joined object60by a given pressing force set beforehand (for example, a given value within the range of 3 kN to 15 kN).

Thus, the first member61and the second member62are sandwiched by the clamp member13and the backing member56, and the clamp member13is biased toward the surface60cof the to-be-joined object60by contraction of the clamp actuator41to generate a clamping force.

Further, in this state, since both the pin member11and the shoulder member12do not move linearly, they “pre-heat” the surface60cof the to-be-joined object60. Thus, the constituent material of the first member61in this contact area is softened by generation of frictional heat, and a plastic flow part60ais caused near the surface60cof the to-be-joined object60.

Next, the controller51drives the linear actuator53so that the tip-end surface11aof the pin member11is sunk with respect to the tip-end surface12aof the shoulder member12(Step S103). At this time, the controller51may drive the linear actuator53(the pin actuator531) so that the pin member11separates from the to-be-joined object60. Further, the controller51may drive the linear actuator53(the shoulder actuator532) so that the shoulder member12is pressed into the to-be-joined object60.

Therefore, the tip-end part of the shoulder member12is pressed into the joining part of the to-be-joined object60while being rotated.

Next, the controller51acquires positional information on the tip-end surface12a(tip end) of the shoulder member12from the position detector33(Step S104). Then, the controller51determines whether the positional information on the tip end of the shoulder member12acquired at Step S104reaches a given first position set beforehand (Step S105).

Here, the first position may be set beforehand based on an experiment etc., and is an arbitrary position within the second member62. In more detail, the first position is an arbitrary position between a contact surface62aof the second member62with the first member61(the surface of the second member62which opposes to the tip-end surface12aof the shoulder member12), and a position 0.3 mm away from the contact surface62a.

Further, in terms of removing the deposit (plating film) or the oxide film formed on the second member62and forming a newly formed surface, the first position may be a position away from the contact surface62aby 0.008 mm or more, or may be a position away from the contact surface62aby 0.01 mm or more. Moreover, in terms of suppressing wear (damage) of the shoulder member12, the first position may be a position away from the contact surface62aby 0.25 mm or less, or may be a position away from the contact surface62aby 0.20 mm or less, or may be a position away from the contact surface62aby 0.10 mm or less.

Further, in terms of removing the deposit (plating film) or the oxide film formed on the second member62and forming the newly formed surface, the first position may be a position away from the deposit (plating film) or the oxide film formed on the second member62by 0.20 mm or less, or may be a position away from the deposit (plating film) or the oxide film formed on the second member62by 0.10 mm or less.

Therefore, the tip-end surface12aof the shoulder member12reaches the arbitrary position away from the contact surface62aof the second member62by 0.3 mm or less (that is, the first position). Further, the newly formed surface is formed in a part of the second member62which is in contact with the shoulder member12, and/or a part of the second member62which is in contact with the plastic flow part60a.

Note that, since the softened material of the plastic flow part60ais pushed away by the shoulder member12, and it flows immediately below the pin member11from immediately below the shoulder member12, the pin member11retreats so that it floats with respect to the shoulder member12(see PROCESS (3) inFIG.5A).

If the controller51determines that the positional information on the tip-end surface12aof the shoulder member12acquired at Step S104has not reached the first position (No at Step S105), it returns to Step S104, and repeats the processings of Steps S104and S105until it determines that the positional information on the tip-end surface12aof the shoulder member12acquired at Step S104reaches the first position.

On the other hand, if the controller51determines that the positional information on the tip-end surface12aof the shoulder member12acquired at Step S104reaches the first position (Yes at Step S105), it performs processing of Step S106.

Note that, if the tip-end surface12aof the shoulder member12reaches the first position, the controller51drives the linear actuator53(the shoulder actuator532) so that the tip-end surface12ais located at the first position. In detail, the controller51drives the linear actuator53so that the advancement of the shoulder member12is stopped.

At Step S106, the controller51measures a period of time “t” after it determines that the tip-end surface12aof the shoulder member12reaches the first position. Next, the controller51determines whether the time t measured at Step S106has passed a given first period of time set beforehand (Step S107).

Here, the first time may be set beforehand by an experiment etc. In terms of making the welding strength of the joining part of the to-be-joined object60high enough, the first time may be, for example, longer than 0 seconds, and it may be 0.5 seconds or more. Further, in terms of shortening the welding time of the to-be-joined object60, the first time may be less than 2 seconds.

If the controller51determines that the time t measured at Step S106has not passed the first time (No at Step S107), it performs the processings of Steps S106and S107until it determines that the time t measured at Step S106passes the first time.

On the other hand, if the controller51determines that the time t measured at Step S106has passed the first time (Yes at Step S107), it performs processing of Step S108.

At Step S108, the controller51drives the linear actuator53(the pin actuator531) so that the pin member11advances toward the to-be-joined object60, and/or the controller51drives the linear actuator53(the pin actuator531) so that the shoulder member12separates from the to-be-joined object60.

In detail, the controller51controls the linear actuator53so that the tip-end surface11aof the pin member11and the tip-end surface12aof the shoulder member12become flush to the extent with almost no height difference.

At this time, in terms of transferring the shape of the tip-end part120to the surface (upper surface)60cof the to-be-joined object60, the controller51may control the linear actuator53so that the tip-end surface11aof the pin member11and the tip-end surface12aof the shoulder member12are located at a given second position set beforehand within the first member61of the to-be-joined object60.

Further, the controller51may control the linear actuator53so that the tip-end surface11aof the pin member11is located at the surface60cof the to-be-joined object60and the tip-end surface12aof the shoulder member12is located at the second position within the first member61of the to-be-joined object60.

Here, the second position can be set beforehand by an experiment etc. In terms of transferring the shape of the tip-end part120to the surface (upper surface)60cof the to-be-joined object60, the second position may be a position, for example, below (inward of) the surface60cof the to-be-joined object60by a dimension corresponding to the height h of the tip-end part120. Further, in terms of reducing the height of irregularity of the surface60cof the to-be-joined object60, the second position may be a position, for example, below (inward of) the surface60cof the to-be-joined object60by a half (½) of the dimension of the height h of the tip-end part120.

Further, in the state where the tip end of the rotating shoulder member12reaches the second position, the controller51may let the shoulder member12stay at the second position for a given second period of time set beforehand. Here, the second time can be set beforehand by an experiment. In terms of transferring the shape of the tip-end part120to the surface (upper surface)60cof the to-be-joined object60, the second time may be, for example, longer than 0 seconds, and it may be 0.5 seconds or more. Further, in terms of shortening the welding time of the to-be-joined object60, the second time may be less than 2 seconds.

Therefore, the pin member11advances gradually toward the first member61, and the shoulder member12retreats from the first member61. At this time, the softened part of the plastic flow part60aflows from immediately below the pin member11to immediately below the shoulder member12(a recess produced by the press-in of the shoulder member12).

Then, the tip-end surface11aof the pin member11and the tip-end surface12aof the shoulder member12move to near the surface60cof the to-be-joined object60. Therefore, the shape of the tip-end part120is stamped onto (transferred to) the surface60cof the to-be-joined object60(see PROCESS (4) inFIG.5B).

Note that, in the processings of Step S103and/or S108, when the area of the tip-end surface of the pin member11is Ap, the area of the tip-end surface of the shoulder member12is As, the pressed-in depth of the pin member11is Pp, and the pressed-in depth of the shoulder member12is Ps, the controller51is preferred to control the linear actuator53so that an absolute value of a tool mean position Tx defined by the following Formula (I) becomes smaller, and it is more preferred to control the linear actuator53so that the tool mean position Tx becomes 0 (Tx=0).
Ap·Pp+As·Ps=Tx(I)
Note that, as for the concrete control for reducing the absolute value of the tool mean position Tx, since it is disclosed in detail in JP2012-196682A, the explanation is omitted herein.

Further, in the processing of Step S108, the controller51may control the linear actuator53so that the tip-end surface11aof the pin member11is located at the first position. In this case, after the tip-end surface11aof the pin member11is located at the first position, the controller51may control the linear actuator53so that the tip-end surface11aof the pin member11and the tip-end surface12aof the shoulder member12become flush.

Next, the controller51drives the linear actuator53so that the pin member11, the shoulder member12, and the clamp member13separate from the to-be-joined object60(Step S109). Then, the controller51controls the rotary actuator57to stop the rotation of the pin member11and the shoulder member12(Step S110; see PROCESS (5) inFIG.5B), and ends this program (welding process of the to-be-joined object60).

Therefore, since the rotation (and the pressing) by the contact of the pin member11and the shoulder member12is no longer applied to the first member61and the second member62, the plastic flow stops in the plastic flow part60a, and the plastic flow part60aand the newly formed surface of the second member62are joined.

Note that the joining part Wa of the to-be-joined object60formed by the friction stirring welding apparatus50according to Embodiment 1 is one example of the joint structure according to Embodiment 1. In detail, an annular recess60bis formed in the joining part Wa of the to-be-joined object60.

Further, in Embodiment 1, since the outer circumferential surface12band the inner circumferential surface12cof the tip-end part120of the shoulder member12incline, an inner wall of the recess60bis formed so as to be bent (see PROCESS (5) inFIG.5B). That is, the shape of the tip-end part120of the shoulder member12is stamped onto (transferred to) the recess60b.

Therefore, according to the shape of the tip-end part120of the shoulder member12, the inner wall of the recess60bcan be formed so that it is inclined, curved, or bent.

In the friction stir spot welding apparatus50according to Embodiment 1 configured in this way, the tip-end part120of the shoulder member12is formed in the tapered shape.

Thus, if the wear does not occur in the tip-end part120of the shoulder member12, the shape of the tip-end part120is stamped onto (transferred to) the surface60cof the to-be-joined object60(joining part) when carrying out the friction stir spot welding of the to-be-joined object60. On the other hand, if the wear occurs in the tip-end part120of the shoulder member12, the shape of the tip-end part120is not stamped onto the surface of the to-be-joined object60, but the surface60cbecomes flat.

Thus, by inspecting (visually inspecting) the surface of the to-be-joined object60after the friction stir spot welding is finished, one can judge whether the tip-end part120of the shoulder member12is worn.

Therefore, it becomes unnecessary to periodically remove the tool (the pin member11, the shoulder member12, and the clamp member13) from the friction stir spot welding apparatus50, and to inspect the abrasion state of the tool.

In the friction stir spot welding apparatus50according to Embodiment 1, since the tip-end part120is formed in the tapered shape, the area of the tip-end surface12aof the shoulder member12becomes smaller, as compared with the conventional shoulder member12without having the taper shape, thereby increasing the surface pressure.

Thus, the friction stir spot welding apparatus50according to Embodiment 1 can shorten the time until the tip-end surface12aof the shoulder member12reaches the first position, as compared with the conventional friction stir spot welding apparatus.

Meanwhile, when the second member62of the to-be-joined object60has a deposit, such as an alloyed hot-dip galvanized steel plate, when it has an oxide film formed on the surface, or when it has sealant material disposed on the surface, it is necessary to remove impurities (for example, zinc etc.) which form the deposit (plating film) or the oxide film, and to form a newly formed surface, in order to join the to-be-joined object60.

In the friction stir spot welding apparatus50according to Embodiment 1, since the tip-end part120is formed in the tapered shape, it can promote a flow of the impurities along the outer circumferential surface12band/or the inner circumferential surface12cof the tip-end part120of the shoulder member12.

Thus, in the friction stir spot welding apparatus50according to Embodiment 1, the time during which the tip-end surface12aof the shoulder member12stays at the first position in order to join the to-be-joined object60with a sufficient welding strength can be 2 seconds or less, as compared with the conventional friction stir spot welding apparatus.

Therefore, in the friction stir spot welding apparatus50according to Embodiment 1, the welding time of the to-be-joined object60can be shortened as compared with the conventional friction stir spot welding apparatus.

The friction stir spot welding apparatus according to Embodiment 1 is the friction stir spot welding apparatus which joins the to-be-joined object by softening it with the frictional heat. The friction stir spot welding apparatus includes the pin member formed in the solid cylindrical shape, the shoulder member which is formed in the hollow cylindrical shape and in which the pin member is inserted, the rotary actuator which rotates the pin member and the shoulder member on the axis which is in agreement with the axial center of the pin member, and the linear actuator which linearly moves each of the pin member and the shoulder member along the axis. The tip-end part of the shoulder member is formed in the tapered shape.

Further, in the friction stir spot welding apparatus according to Embodiment 1, the tip-end surface of the shoulder member and the tip-end surface of the pin member may be in agreement with each other, when seen horizontally.

Moreover, in the friction stir spot welding apparatus according to Embodiment 1, the outer circumferential surface of the tip-end part of the shoulder member may be inclined, curved, or bent.

Further, in the friction stir spot welding apparatus according to Embodiment 1, the outer circumferential surface of the tip-end part of the shoulder member may be inclined, and the tip-end part of the shoulder member may be configured so that the angle formed between the tip-end surface of the shoulder member and the inclined surface of the shoulder member is 6° or more and less than 45°, when seen horizontally.

Moreover, in the friction stir spot welding apparatus according to Embodiment 1, the inner circumferential surface of the tip-end part of the shoulder member may be inclined, curved, or bent.

Further, in the friction stir spot welding apparatus according to Embodiment 1, the inner circumferential surface of the tip-end part of the shoulder member may be inclined, and the tip-end part of the shoulder member may be configured so that the angle formed between the tip-end surface of the shoulder member and the inclined surface of the shoulder member is 6° or more and less than 45°, when seen horizontally.

Further, in the friction stir spot welding apparatus according to Embodiment 1, the to-be-joined object may include the first member and the second member, the first member being disposed so that it opposes to the pin member and the shoulder member, and being made of the material with the melting point lower than the second member. The friction stir spot welding apparatus may further be provided with the controller. The controller may be adapted to perform:(A) in which the rotary actuator and the linear actuator are operated so that the pin member and the shoulder member press the joining part of the to-be-joined object, while the pin member and the shoulder member rotate;(B) in which the linear actuator and the rotary actuator are operated so that the tip end of the rotating shoulder member reaches the given first position set beforehand within the second member, and the rotating pin member retreats from the joining part of the to-be-joined object;(C) in which, after (B), the tip end of the rotating shoulder member stays in a state where the tip end of the shoulder member reaches the first position, for the given first time set beforehand; and(D) in which, after (C), the rotary actuator and the linear actuator are operated so that the rotating shoulder member is drawn out from the joining part of the to-be-joined object, and the rotating pin member is advanced toward the joining part of the to-be-joined object.

Further, in the friction stir spot welding apparatus according to Embodiment 1, when performing (D), the controller may operate the rotary actuator and the linear actuator so that the tip end of the shoulder member reaches the given second position set beforehand within the first member.

Further, in the friction stir spot welding apparatus according to Embodiment 1, in (D), the controller may cause the tip end of the rotating shoulder member to stay in the state where the tip end of the shoulder member has reached the second position for the given second time set beforehand.

Further, in the friction stir spot welding apparatus according to Embodiment 1, after (D), the controller may perform (E) in which the rotary actuator and the linear actuator are operated so that the rotating pin member and the rotating shoulder member are drawn out from the joining part of the to-be-joined object.

Further, in the friction stir spot welding apparatus according to Embodiment 1, the joining part may further include the third member disposed between the first member and the second member.

Further, in the friction stir spot welding apparatus according to Embodiment 1, the first time may be a period of time for 0 seconds or more and less than 2 seconds.

Further, in the friction stir spot welding apparatus according to Embodiment 1, the first position may be a position away from the principal surface of the second member on the side which opposes to the tip-end surface of the shoulder member, by 0.3 mm or less.

Further, the joint structure according to Embodiment 1 is the joint structure which is formed by the friction stir spot welding apparatus carrying out friction stir spot welding of the to-be-joined object including the first member and the second member at the joining part. The first member is made of material with the melting point lower than the second member. The first member and the second member are disposed in this order. The annular recess is formed in the surface of the joining part. The bottom surface of the recess is inclined, curved, or bent.

Further, in the joint structure according to Embodiment 1, the friction stir spot welding apparatus may be provided with the pin member formed in the solid cylindrical shape and the shoulder member formed in the hollow cylindrical shape, the pin member being inserted. The joint structure may be formed by the tip end of the shoulder member while being rotated staying in the state where the tip end of the shoulder member reaches the given first position set beforehand within the second member, for the given first period of time set beforehand.

[Modification 1]

Next, a modification of the friction stir spot welding apparatus50according to Embodiment 1 is described.

FIG.6is a schematic diagram in which a substantial part of a friction stir spot welding apparatus of Modification 1 of Embodiment 1 is enlarged.FIGS.6(A) to6(D)illustrate aspects in which the outer circumferential surface of the tip-end part of the shoulder member is formed so that it is inclined, curved, or bent.FIGS.6(E) to6(H)illustrate aspects in which the inner circumferential surface of the tip-end part of the shoulder member is formed so that it is inclined, curved, or bent.

As illustrated inFIG.6(A), as for the friction stir spot welding apparatus50of Modification 1, the outer circumferential surface12bof the tip-end part120of the shoulder member12may be formed so that it is inclined. In more detail, the cross-sectional shape of the outer circumferential surface12bof the tip-end part120(a cross section along the axis Xr) when seen horizontally may be formed so that it is inclined with respect to the axis Xr.

As illustrated inFIG.6(B), as for the friction stir spot welding apparatus50of Modification 1, the outer circumferential surface12bof the tip-end part120of the shoulder member12may be formed so that it is bent. In more detail, the cross-sectional shape of the outer circumferential surface12bof the tip-end part120may be formed so that it is bent when seen horizontally. Note that, although inFIG.6(B)the number of bending points is one, the number of bending points may be two or more.

Further, as illustrated inFIG.6(C), as for the friction stir spot welding apparatus50of Modification 1, the outer circumferential surface12bof the tip-end part120of the shoulder member12may be formed so that it is curved (in an arc). In more detail, the cross-sectional shape of the outer circumferential surface12bof the tip-end part120may be formed so that it is curved when seen horizontally.

Further, as illustrated inFIG.6(D), as for the friction stir spot welding apparatus50of Modification 1, the outer circumferential surface12bof the tip-end part120of the shoulder member12may be formed so that it is curved. In more detail, the cross-sectional shape of the outer circumferential surface12bof the tip-end part120may be formed so that it is curved when seen horizontally. Here, the term “curve” of the “being curved” is a curve of a function represented by a higher-order function, such as a quadratic function or a cubic function, an exponential function, or a logarithmic function.

Further, as illustrated inFIG.6(E), as for the friction stir spot welding apparatus50of Modification 1, the inner circumferential surface12cof the tip-end part120of the shoulder member12may be formed so that it is inclined. In more detail, the cross-sectional shape of the inner circumferential surface12cof the tip-end part120(a cross section along the axis Xr) may be formed so that it is inclined to the axis Xr when seen horizontally.

Further, as illustrated inFIG.6(F), as for the friction stir spot welding apparatus50of Modification 1, the inner circumferential surface12cof the tip-end part120of the shoulder member12may be formed so that it is bent. In more detail, the cross-sectional shape of the inner circumferential surface12cof the tip-end part120may be formed so that it is bent when seen horizontally. Note that, although inFIG.6(F)the number of bending points is one, the number of bending points may be two or more.

Further, as illustrated inFIG.6(G), as for the friction stir spot welding apparatus50of Modification 1, the inner circumferential surface12cof the tip-end part120of the shoulder member12may be formed so that it is curved (in an arc). In more detail, the cross-sectional shape of the inner circumferential surface12cof the tip-end part120may be formed so that it is curved when seen horizontally.

Further, as illustrated inFIG.6(H), as for the friction stir spot welding apparatus50of Modification 1, the inner circumferential surface12cof the tip-end part120of the shoulder member12may be formed so that it is curved. In more detail, the cross-sectional shape of the inner circumferential surface12cof the tip-end part120may be formed so that it is curved when seen horizontally. Here, the term “curve” of the “being curved” is a curve of a function represented by a higher-order function, such as a quadratic function or a cubic function, an exponential function, or a logarithmic function.

The friction stir spot welding apparatus50of Modification 1 configured in this way also has similar operation and effects to the friction stir spot welding apparatus50according to Embodiment 1.

Embodiment 2

A friction stir spot welding apparatus according to Embodiment 2 is configured so that the tip-end surface of the shoulder member of the friction stir spot welding apparatus according to Embodiment 1 (including its modifications) projects more than the tip-end surface of the pin member when seen horizontally.

Below, one example of the friction stir spot welding apparatus according to Embodiment 2 is described in detail with reference to the drawings.

[Configuration of Friction Stir Spot Welding Apparatus]

FIG.7is a schematic diagram illustrating an outline configuration of a substantial part of the friction stir spot welding apparatus according to Embodiment 2.

As illustrated inFIG.7, the friction stir spot welding apparatus50according to Embodiment 2 has the same fundamental configuration as the friction stir spot welding apparatus50according to Embodiment 1, but it differs in that the tip-end surface12aof the shoulder member12is configured to project more than the tip-end surface11aof the pin member11when seen horizontally.

Note that, inFIG.7, the outer circumferential surface12band the inner circumferential surface12cof the tip-end part120of the shoulder member12are formed so that they are inclined when seen horizontally.

Further, the outer circumferential surface12band the inner circumferential surface12cof the tip-end part120of the shoulder member12may be formed at the same inclination angle when seen horizontally. Moreover, an inclination angle α of the outer circumferential surface12bof the tip-end part120may be larger than an inclination angle β of the inner circumferential surface12cof the tip-end part120. Alternatively, the inclination angle α of the outer circumferential surface12bof the tip-end part120may be smaller than the inclination angle β of the inner circumferential surface12cof the tip-end part120.

Here, the inclination angle α of the outer circumferential surface12bof the tip-end part120and the inclination angle β of the inner circumferential surface12cof the tip-end part120are described with reference toFIGS.8A and8B.

FIG.8Ais a schematic diagram illustrating an outline configuration of the tip-end parts of the pin member, the shoulder member, and the clamp member of the friction stir spot welding apparatus.FIG.8Bis a view in which a shearing force which acts on the transferring part of the to-be-joined object is broken down.

As illustrated inFIG.8A, a part of the joining part Wa of the to-be-joined object60to which the shape of the outer circumferential surface12bof the tip-end part120of the shoulder member12is transferred is a transferring part601. Further, a protruded part formed in the joining part Wa of the to-be-joined object60by the inner circumferential surface12cof the tip-end part120of the shoulder member12and the tip-end part of the pin member11is a transferring part602.

Note that the inclination angle α of the outer circumferential surface12bof the tip-end part120is an angle formed between an imaginary line C which is a line perpendicular to the axis Xr and a line which connects an end A1on the base-end side (upper-end side) where the outer circumferential surface12bis inclined and an end A2on the tip-end side (lower-end side).

Similarly, the inclination angle β of the inner circumferential surface12cof the tip-end part120is an angle formed between the imaginary line C and a line which connects an end B1on the base-end side (upper-end side) where the inner circumferential surface12cis inclined and an end B2on the tip-end side (lower-end side).

Thus, as for the outer circumferential surface12band the inner circumferential surface12cof the tip-end part120, when they are, for example, curved, as illustrated in the modification of Embodiment 1, the lines which connect the base-end part and the tip-end part of the curve etc., with the imaginary line C, correspond to the inclination angle α and the inclination angle β, respectively.

As illustrated by a one-dot chain line inFIG.8A, as the inclination angle α of the outer circumferential surface12bincreases, an angle θ1of the inclined surface of the transferring part601also increases. As the angle θ1of the inclined surface of the transferring part601increases, the base of the transferring part601(an area of the bottom surface) decreases, and the transferring part601may be partially missing (torn).

Similarly, as the inclination angle β of the inner circumferential surface12cincreases, an angle θ2of the inclined surface of the transferring part602also increases. As the angle θ2of the inclined surface of the transferring part602increases, the base of the transferring part602(an area of the bottom surface) decreases, and the transferring part602may be partially missing (torn).

Further, when separating the tip-end part of the pin member11and the tip-end part of the shoulder member12from the to-be-joined object60, shearing forces F1 and F2 act on the inclined surface of the transferring part601(a contact surface with the outer circumferential surface12b) and the inclined surface of the transferring part602(a contact surface with the inner circumferential surface12c), respectively.

As illustrated inFIG.8B(1), F1 sin θ1acts as a force which partially tears off the transferring part601. Similarly, F2 sin θ2acts as a force which partially tears off the transferring part602(seeFIG. B8(2)). Here, when θ1=45°, F1 sin θ1=F1 cos θ1. Similarly, when θ2=45°, F2 sin θ2=F2 cos θ2. Further, θ1=inclination angle α, and θ2=inclination angle β.

Thus, when θ1<45° (i.e., the inclination angle α<45°), generation of the partial tearing-off of the transferring part601can be suppressed. Similarly, when θ2<45° (i.e., the inclination angle β<45°), generation of the partial tearing-off of the transferring part602can be suppressed.

Therefore, the inclination angle α of the outer circumferential surface12bof the tip-end part120is preferably less than 45°, and the inclination angle β of the inner circumferential surface12cof the tip-end part120is preferably less than 45°.

Further, from the results of Test Example 1 and Test Example 2 which will be described later, the inclination angle α may be 32° or less, or may be 17° or less, or may be 12° or less, or may be 6° or less. Similarly, the inclination angle β may be 32° or less, or may be 17° or less, or may be 12° or less, or may be 6° or less.

The friction stir spot welding apparatus50according to Embodiment 2 configured in this way also has similar operation and effects to the friction stir spot welding apparatus50according to Embodiment 1.

Embodiment 3

A friction stir spot welding apparatus according to Embodiment 3 is a friction stir spot welding apparatus which joins the to-be-joined object by softening it with the frictional heat. The friction stir spot welding apparatus includes the pin member formed in the solid cylindrical shape, the shoulder member which is formed in the hollow cylindrical shape and in which the pin member is inserted, the rotary actuator which rotates the pin member and the shoulder member on the axis which is in agreement with the axial center of the pin member, and the linear actuator which linearly moves each of the pin member and the shoulder member along the axis. A recess extending in the circumferential direction is formed in the tip-end surface of the shoulder member.

Below, one example of the friction stir spot welding apparatus according to Embodiment 3 is described in detail with reference to the drawings.

[Configuration of Friction Stir Spot Welding Apparatus]

FIG.9is a schematic diagram illustrating an outline configuration of a substantial part of the friction stir spot welding apparatus according to Embodiment 3.

As illustrated inFIG.9, the friction stir spot welding apparatus50according to Embodiment 3 has the same fundamental configuration as the friction stir spot welding apparatus50according to Embodiment 1, but it differs in that a recess20extending in the circumferential direction (annularly) is formed in the tip-end surface12aof the shoulder member12.

The recess20may be formed so that the area of an opening20A becomes larger than the area of a bottom surface20B. Further, among an inner circumferential surface20C and an outer circumferential surface20D of the recess20, at least one circumferential surface may be formed so that it is parallel to the axis Xr. Moreover, among the inner circumferential surface20C and the outer circumferential surface20D of the recess20, at least one circumferential surface may be formed so that it is inclined, curved, or bent.

Further, in terms of stamping (transferring) the shape of the tip-end part120onto the surface of the to-be-joined object60, a depth d of the recess20may be 0.05 mm or more, or may be 5% or more of the thickness of the first member61, for example. Moreover, in terms of suppressing the damage of the tip-end part120of the shoulder member12, the depth d may be 0.5 mm or less, or may be 50% or less of the thickness of the first member61, for example.

The friction stir spot welding apparatus50according to Embodiment 3 configured in this way also has similar operation and effects to the friction stir spot welding apparatus50according to Embodiment 1.

Note that, although in Embodiment 3 the recess20is formed in the tip-end surface12aof the shoulder member12, it is not limited to this configuration. An annular recess20may be formed in the tip-end surface11aof the pin member11.

Test Examples

Next, joining tests of the to-be-joined object60by the friction stir spot welding apparatus50according to Embodiment 2 and the friction stir spot welding method disclosed in Patent Document 1 are described.

Test Example 1

The joining test of the to-be-joined object60is performed using the friction stir spot welding apparatus50according to Embodiment 2. Note that, in Test Example 1, the height of the tip-end part120is 0.2 mm. Further, the inclination angle α of the outer circumferential surface12bof the tip-end part120is 12°, and the inclination angle β of the inner circumferential surface12cof the tip-end part120is 32°.

Test Example 2

The joining test of the to-be-joined object60is performed using the friction stir spot welding apparatus50according to Embodiment 2. Note that, in Test Example 2, the height of the tip-end part120is 0.1 mm. Further, the inclination angle α of the outer circumferential surface12bof the tip-end part120is 6°, and the inclination angle β of the inner circumferential surface12cof the tip-end part120is 17°.

Comparative Example

As a comparative example, the joining test of the to-be-joined object60is performed by the friction stir spot welding method disclosed in Patent Document 1. In detail, as a friction stir spot welding apparatus of Comparative Example, the joining test of the to-be-joined object60is performed using a shoulder member12formed so that the inner circumferential surface and the outer circumferential surface of the tip-end part120become parallel to the axis Xr.

(Welding Conditions)

As the first member61, a 1 mm aluminum plate (A6061) is used, and as the second member62, a 1.2 mm 980 MPa-class alloyed hot-dip galvanized steel plate (GA) is used.

Note that, in Test Example 1, the first position which is a target arrival position of the shoulder member12is set as a position which is 0.3 mm below the contact surface (upper surface) of the second member62with the first member61. Further, in Test Example 2, it is set as a position which is 0.2 mm below the contact surface (upper surface) of the second member62with the first member61. Moreover, in Comparative Example, the first position which is the target arrival position of the shoulder member12is set as a position which is 0.1 mm below the contact surface (upper surface) of the second member62with the first member61.

Further, while changing the time (the first time) for which the tip-end surface12aof the shoulder member12stays at the first position after the tip-end surface12areached the first position between 0, 1, 2, and 3 seconds, the to-be-joined object60is joined. Moreover, the first rotational speed which is a rotational speed of the pin member11and the shoulder member12is set as 2,000 rpm.

Then, a tensile-shearing test (JIS Z 3136) and a cross-tensile test (JIS Z 3137) of the to-be-joined objects60which were joined by each of the friction stir spot welding apparatuses of Test Examples 1 and 2, and Comparative Example were performed.

(Test Results)

FIG.10illustrates graphs of the results of the tensile-shearing test and the cross-tensile test of the to-be-joined objects which are friction stir spot welded under the above-described welding conditions using the friction stir spot welding apparatuses of Test Examples 1 and 2, and Comparative Example. Further,FIG.11illustrates a cross-sectional photograph of the to-be-joined object which is friction stir spot welded using the friction stir spot welding apparatus of Test Example 1.

As illustrated inFIG.10, as the friction stir spot welding was carried out using the friction stir spot welding apparatus of Comparative Example, it was not able to obtain a sufficient welding strength when the first time was 0 seconds. Further, in the tensile-shearing test (TSS) of the friction stir spot welding apparatus of Comparative Example, a sufficient welding strength was obtained when the first time was 1 second, but in the cross-tensile test (CTS), a sufficient welding strength was not obtained unless the first time was 2 seconds or more.

On the other hand, when the friction stir spot welding was carried out using the friction stir spot welding apparatuses of Test Examples 1 and 2, a sufficient welding strength was obtained even when the first time was 0 seconds.

Based on these results, the friction stir spot welding apparatus50according to Embodiment 1 demonstrated that the to-be-joined object60could be joined with the sufficient welding strength when setting the first time as 0 seconds or more and less than 2 seconds.

Further, as illustrated inFIG.11, in a case where the wear does not occur in the tip-end part120of the shoulder member12when the friction stir spot welding was carried out using the friction stir spot welding apparatus of Test Example 1, it was demonstrated that the shape of the tip-end part120(the tapered shape; the transferring part) was stamped onto (transferred to) the surface60cof the to-be-joined object60(joining part).

It is apparent for the person skilled in the art that many improvements or other embodiments of the present disclosure are possible from the above description. Therefore, the above description is to be interpreted only as illustration, and it is provided in order to teach the person skilled in the art the best mode for implementing the present disclosure. The details of the structures and/or the functions may be changed substantially, without departing from the present disclosure. Moreover, various inventions may be formed by suitable combinations of the plurality of components disclosed in the above embodiments.

INDUSTRIAL APPLICABILITY

The friction stir spot welding apparatus of the present disclosure is useful because one can judge the abrasion state of the tool based on the joining spot of the to-be-joined object (the surface of the joining part).