CN114799484A

CN114799484A - Friction stir spot welding device and control method thereof

Info

Publication number: CN114799484A
Application number: CN202210635565.1A
Authority: CN
Inventors: 王志勇; 石姚林; 牛得学
Original assignee: Binzhou University
Current assignee: Binzhou University
Priority date: 2022-06-07
Filing date: 2022-06-07
Publication date: 2022-07-29

Abstract

The invention discloses a friction stir spot welding device and a control method thereof, which comprises a stirring pin and a stirring sleeve which are in insertion fit, the stirring sleeve power motor is connected with a first-stage gear, the stirring sleeve is connected with a second-stage gear, the first-stage gear is meshed with the second-stage gear, a stirring pin is fixedly connected with an output shaft of the main shaft motor in the circumferential direction and is in axial sliding fit with the output shaft of the main shaft motor, an upper moving plate is fixedly connected with the stirring pin in the circumferential direction and is fixedly connected with the stirring pin in the axial direction, a lower moving plate is fixedly connected with the stirring sleeve in the circumferential direction and is fixedly connected with the stirring sleeve in the axial direction, the upper moving plate and the lower moving plate are both in threaded connection with a lead screw, the matching thread turning directions of the lead screw and the upper moving plate and the lower moving plate are opposite, the lead screw is connected with an axial driving motor, and the axial length of the meshing surface of the first-stage gear and the second-stage gear is larger than the axial movement range of the upper moving plate. The invention can automatically carry out the work of the stirring stage and the backfilling stage, and solves the keyhole problem of friction stir welding.

Description

Friction stir spot welding device and control method thereof

Technical Field

The invention relates to the technical field of friction stir welding, in particular to a friction stir spot welding device and a control method thereof.

Background

The friction stir welding has the same principle as the conventional friction welding, and also utilizes frictional heat and plastic deformation heat as a welding heat source. The difference is that the friction stir welding process is that a cylindrical or other stirring pin extends into the joint of the workpieces, and the stirring pin is rubbed with the workpieces to be welded through high-speed rotation, so that the connecting parts of the workpieces to be welded are locally melted and connected. In the welding process, as the stirring pin extends into the welding seam of the workpiece while rotating, a keyhole is left at the tail end of the welding seam when the welding process is finished, the attractiveness of the surface of the welding seam is influenced, and the mechanical property of the welding seam is reduced to a certain extent, so that the keyhole is very necessary to be repaired in the engineering application process.

For the friction stir welding with some structures, a welding starting plate and a lead-out plate can be arranged at the welding starting and welding withdrawing positions, so that a keyhole is not left on a workpiece; or a welding key hole for friction stir welding is led out from the opening of the product part, for example, a key hole is led out from an opening frame on the cabin body and then is machined and removed, but the method is not suitable for circular seam welding of a rotary structure and the like.

For the friction stir welding of the thin plates, a pin-free stirring head can be used for welding, and a large amount of friction heat is generated only by the interaction between a rotating shaft shoulder and metal on the surface of a weldment in the welding process, so that the flowing and mixing of the metal inside are promoted, and a solid-phase connecting joint is formed. The cross-sectional shape of the shoulder is critical due to the lack of stirring action of the pin. Although no keyhole is generated by adopting the method, the applicable structure of the method is seriously limited, and the mechanical property of the joint is reduced because the friction and the stirring action between the stirring head and the base material are weakened. When the keyhole is repaired by the friction stir welding method, the keyhole appears again at another position, so that the repair is also limited.

Therefore, in the prior art, the keyhole of friction stir welding not only needs to be repaired, but also the method or the structure adopted for repairing the keyhole is severely limited, and particularly for friction stir spot welding, the repairing process and the repairing difficulty are severely limited by the structure of the workpiece to be welded, the aesthetic property of the welding surface and the mechanical property of the welding line.

Disclosure of Invention

Aiming at the defects in the background technology, the invention provides a friction stir spot welding device and a control method thereof, which solve the technical problem that the friction stir welding quality is severely restricted by the structure of a workpiece to be welded, the attractiveness of the welding surface and the mechanical property of a welding line.

The technical scheme of the application is as follows:

the utility model provides a friction stir spot welding device, includes actuating mechanism, drive mechanism and friction stir mechanism, friction stir mechanism is including alternating complex stirring needle and stirring cover, friction stir mechanism include with stirring cover rotation complex clamp ring, actuating mechanism includes spindle motor and stirring cover motor power, actuating mechanism includes the one-level gear that links to each other with stirring cover motor power, the second grade gear that links to each other with the stirring cover, one-level gear and second grade gear engagement, circumference fixed connection and axial sliding fit between the output shaft of stirring needle and spindle motor, stirring needle circumference rotation connection and axial fixedly connected with move up the board, stirring cover circumference rotation connection and axial fixedly connected with move down the board, go up move down the board all with lead screw threaded connection, lead screw and move up the board, the movable board, The screw threads matched with the lower moving plate are opposite in rotating direction, the screw rod is connected with an axial driving motor, and the axial length of the meshing surface of the primary gear and the secondary gear is larger than the axial movement range of the upper moving plate.

Further, the screw rod comprises a first screw rod and a second screw rod which are coaxially connected and have opposite thread turning directions, the upper moving plate is in threaded connection with the first screw rod, the lower moving plate is in threaded connection with the second screw rod, and the first screw rod or the second screw rod is connected with the axial driving motor.

Furthermore, the first screw rod is in threaded connection with the left side of the upper moving plate, the second screw rod is in threaded connection with the left side of the lower moving plate, the right side of the upper moving plate is in threaded connection with a third screw rod, the right side of the lower moving plate is in threaded connection with a fourth screw rod, the third screw rod is in coaxial connection with the fourth screw rod, the thread turning directions of the third screw rod and the fourth screw rod are opposite, and the third screw rod or the fourth screw rod is connected with a motor synchronous with the axial driving motor.

Further, the upper moving plate and the lower moving plate are in a structure which is bilaterally symmetrical about the stirring pin, the first screw rod and the third screw rod are bilaterally symmetrical, and the second screw rod and the fourth screw rod are bilaterally symmetrical.

Or the right side of the upper moving plate is in threaded connection with a third screw rod, the right side of the lower moving plate is in threaded connection with a fourth screw rod, the third screw rod and the fourth screw rod are coaxially connected, the thread turning directions are opposite, and a synchronous transmission mechanism is arranged between the first screw rod and the third screw rod or/and between the second screw rod and the fourth screw rod.

Furthermore, the synchronous rotating mechanism comprises belt wheels which are respectively arranged on the first screw rod and the third screw rod or/and the second screw rod and the fourth screw rod, and the left belt wheel and the right belt wheel which are opposite are connected through a transmission belt.

Or the synchronous rotating mechanism comprises chain wheels which are respectively arranged on the first screw rod and the third screw rod or/and the second screw rod and the fourth screw rod, and the left belt wheel and the right belt wheel which are opposite are connected through a transmission chain.

Furthermore, the driving mechanism and the transmission mechanism are arranged in the machine shell, the machine shell is detachably connected with a machine body cover, the compression ring is connected with the machine body cover or/and the machine shell and extends out of the machine body cover, and the end part of the lead screw is in rotary fit with the compression ring through a bearing.

Further, the spindle motor and the stirring sleeve power motor are arranged at the same height and are arranged in the shell through the motor base, the axial driving motor is arranged in the shell above the spindle motor, the stirring pin is connected with an output shaft of the spindle motor through a sliding coupling, and the primary gear is connected with the stirring sleeve power motor through a gear driving shaft.

A control method of a friction stir spot welding device comprises a compaction stage, a stirring stage, a backfill stage and a demoulding stage;

in the compaction stage, the working surfaces of the stirring pin, the stirring sleeve and the compaction ring are controlled to be in contact with the upper surface of the plate to be connected, and the compaction ring is controlled to apply pressure downwards all the time;

in the stirring stage, a spindle motor and an axial driving motor are controlled to start, the spindle motor drives a stirring pin to rotate, the axial driving motor drives a screw rod to rotate forward, the screw rod drives an upper moving plate and a lower moving plate to move synchronously, the stirring pin is driven by the spindle motor and the upper moving plate to rotate and simultaneously gradually presses down, the stirring pin is rubbed with an upper plate material of a plate material to be connected, the stirring sleeve is driven by the lower moving plate to move up while pressing down, a flowing space is provided for a molten material which is rubbed with the plate material to be connected, and the space generated by the movement of the stirring pin on the stirring sleeve is gradually filled with the molten material which is rubbed;

in the backfilling stage, after the stirring pin is pressed downwards and stirred, the axial driving motor is controlled to drive the screw rod to rotate reversely, the screw rod drives the upper moving plate to move upwards to drive the stirring pin to return upwards, the stirring pin is withdrawn relative to the plate to be connected, meanwhile, the screw rod drives the lower moving plate to move downwards to drive the stirring sleeve to press downwards, meanwhile, the stirring sleeve is driven by the stirring sleeve power motor to rotate, the material in a molten state flowing out in the stirring stage is pressed back into a groove generated by withdrawing the stirring pin, and the groove generated by the stirring pin is filled until the stirring pin, the stirring sleeve and the compression ring return to the initial positions;

and in the die stripping stage, the die stripping is started after the backfilling stage is finished, the welding device leaves the surface of the plate to be connected, and the whole welding work is finished.

Compared with the prior art, the friction stir spot welding device and the control method thereof can effectively solve the problem of keyhole generated during friction stir spot welding of various plates, under the action of the screw rod driven by the axial driving motor, the upper moving plate and the lower moving plate can synchronously move to enable the stirring needle and the stirring sleeve to axially move in opposite directions, so that the friction stir spot welding automatically carries out the work of a stirring stage and a backfilling stage, thereby providing a flowing space for a material to be connected with the plates to be rubbed and melted, and pressing the material flowing out in the stirring stage in a melting state back to a groove generated by the stirring needle in the backfilling stage.

Drawings

In order to illustrate the embodiments of the invention more clearly, the drawings that are needed in the description of the embodiments will be briefly described below, it being apparent that the drawings in the following description are only some embodiments of the invention, and that other drawings may be derived from those drawings by a person skilled in the art without inventive effort.

FIG. 1 is a schematic structural view of a driving mechanism, a transmission mechanism and a friction stir mechanism;

FIG. 2 is an enlarged view of a portion of the structure of FIG. 1;

FIG. 3 is a front view of the agitator sleeve of FIG. 2 shown in a retracted position;

FIG. 4 is a front view of the agitator sleeve of FIG. 2 shown extended;

FIG. 5 is a cross-sectional view of the pin of FIG. 2 as it is withdrawn;

FIG. 6 is an enlarged view of the moving mechanism of the upper moving plate and the lower moving plate in FIG. 1;

FIG. 7 is a cross-sectional view of the friction stir mechanism with the stir pin extended;

FIG. 8 is a cross-sectional view of view one of the present invention;

FIG. 9 is a cross-sectional view from perspective two of the present invention;

reference numbers in the figures: 1-a main shaft motor, 2-a stirring sleeve power motor, 3-a first coupler, 4-a gear driving shaft, 5-a primary gear, 6-a secondary gear, 7-a sliding coupler, 8-a stirring pin, 9-a stirring sleeve, 10-an axial driving motor, 11-a transmission chain, 12-a first screw rod, 13-a stirring pin bearing, 14-a first screw rod coupler, 15-a stirring sleeve bearing, 16-a second screw rod, 17-a bearing, 18-a fourth screw rod, 19-a lower moving plate, 20-a second screw rod coupler, 21-an upper moving plate, 22-a third screw rod, 23-a chain wheel, 24-a pressing ring, 25-a screw rod driving shaft, 26-a second coupler, 27-a machine body shell and 28-a machine body cover, 29-motor base, 30-third coupling and 31-lubricating medium filling hole.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.

Embodiment 1, a friction stir spot welding apparatus, as shown in fig. 1 to 5, includes a driving mechanism, a transmission mechanism, and a friction stir mechanism, the friction stir mechanism includes a pin 8 and a sleeve 9 that are inserted and engaged, the pin 8 can rotate relative to the sleeve 9 within the sleeve 9, and naturally the sleeve 9 can also rotate relative to the pin 8, that is, the sleeve 9 and the pin 8 can rotate around their axes independently of each other. The friction stir mechanism further comprises a compression ring 24 in rotary fit with the stirring sleeve 9, the compression ring 24 is fixedly arranged, the stirring sleeve 9 can rotate relative to the compression ring 24, and a lubricating medium filling hole 31 leading to the inner wall of the compression ring 24 and the outer wall of the stirring sleeve 9 is formed in the compression ring 24.

The driving mechanism comprises a spindle motor 1 and a stirring sleeve power motor 2, the spindle motor 1 is used for driving a stirring pin 8 to rotate, and the stirring sleeve power motor 2 is used for driving a stirring sleeve 9 to rotate. The transmission mechanism comprises a primary gear 5 connected with the stirring sleeve power motor 2 and a secondary gear 6 connected with the stirring sleeve 9, and the primary gear 5 is meshed with the secondary gear 6. That is, the rotary power output by the output shaft of the stirring sleeve power motor 2 can be transmitted to the stirring sleeve 9 through the primary gear 5 and the secondary gear 6, and then the stirring sleeve 9 is driven to rotate. Specifically, the output shaft of the stirring sleeve power motor 2 is connected with a gear driving shaft 4 through a first coupler 3, the gear driving shaft 4 is connected with the primary gear 5, and the secondary gear 6 is fixedly connected with the stirring sleeve 9.

Circumference fixed connection and axial sliding fit between the output shaft of stirring needle 8 and spindle motor 1, specifically, spindle motor 1's output shaft passes through slip coupling 7 and links to each other with stirring needle 8, and when spindle motor 1 drive stirring needle 8 was rotatory, stirring needle 8 can be relative spindle motor 1 axial motion.

As shown in fig. 6, the stirring pin 8 is circumferentially and rotatably connected and axially and fixedly connected with an upper moving plate 21, specifically, the upper moving plate 21 is connected with the upper moving plate 21 through a stirring pin bearing 13, an outer ring of the stirring pin bearing 13 is fixedly connected with the upper moving plate 21, and an inner ring of the stirring pin bearing 13 is fixedly connected with the stirring pin 8. Therefore, when the mixing pin 8 rotates relative to the upper moving plate 13, the axial movement of the mixing pin 8 carried by the upper moving plate 21 is not affected.

Similarly, the stirring sleeve 9 is connected with a lower moving plate 19 in a circumferential rotation manner and is axially and fixedly connected with the stirring sleeve 9, specifically, the lower moving plate 19 is connected with the stirring sleeve 9 through a stirring sleeve bearing 15, an outer ring of the stirring sleeve bearing 15 is fixedly connected with the lower moving plate 19, and an inner ring of the stirring sleeve bearing 15 is fixedly connected with the stirring sleeve 9. Therefore, when the stirring sleeve 9 rotates relative to the lower moving plate 15, the axial movement of the stirring sleeve 9 carried by the lower moving plate 19 is not affected.

The upper moving plate 21 and the lower moving plate 19 are both in threaded connection with a screw rod, the screw rod is opposite to the thread turning direction matched with the upper moving plate 21 and the lower moving plate 19, and the screw rod is connected with an axial driving motor 10. Specifically, as shown in fig. 9, the axial driving motor 10 is connected to a lead screw driving shaft 25 through a second coupling 26, the lead screw driving shaft 25 is connected to the lead screw through a third coupling 30, and of course, the axial driving motor 10 may also be directly connected to the lead screw through the coupling. When the axial driving motor 10 drives the screw rod to rotate, because the axial position of the screw rod is not changed, the upper moving plate 21 and the lower moving plate 19 connected with the screw rod can synchronously move axially, and the moving directions of the upper moving plate 21 and the lower moving plate 19 are opposite, so that the stirring needle 8 and the stirring sleeve 9 can be driven to do axial movement deviating from each other, when the stirring needle 8 moves downwards, the stirring sleeve 9 moves upwards, and when the stirring needle 8 moves upwards, the stirring sleeve 9 moves downwards.

It should be particularly noted that the axial length of the meshing surface of the primary gear 5 and the secondary gear 6 is greater than the axial movement range of the upper moving plate 21. When the stirring sleeve 9 moves up and down, no matter the stirring sleeve moves to any position, the stirring sleeve power motor 2 can drive the stirring sleeve 9 to rotate circumferentially.

Example 2, a friction stir spot welding device, on the basis of example 1, the screw rod is designed as two screw rods connected to each other. Namely, the screw rod comprises a first screw rod 12 and a second screw rod 16 which are coaxially connected and have opposite thread turning directions, and the first screw rod 12 and the second screw rod 16 are connected through a first screw rod coupler, so that the processing, the manufacturing and the assembly are convenient. The upper moving plate 21 is in threaded connection with the first screw rod 12, the lower moving plate 19 is in threaded connection with the second screw rod 16, and the first screw rod 12 or the second screw rod 16 is connected with the axial driving motor 10.

In embodiment 3, in addition to embodiment 2, the first screw 12 is screwed to the left side of the upper moving plate 21, the second screw 16 is screwed to the left side of the lower moving plate 19, the right side of the upper moving plate 21 is screwed to the third screw 22, the right side of the lower moving plate 19 is screwed to the fourth screw 18, the third screw 22 and the fourth screw 18 are coaxially connected and have opposite screwing directions, and the third screw 22 or the fourth screw 18 is connected to a motor synchronized with the axial driving motor 10. Two sets of screw rods are arranged and driven by two synchronously controlled motors, so that the motion stability of the upper movable plate 21 and the lower movable plate 19 can be fully ensured, and the quality of friction stir spot welding is further ensured.

Further, the upper moving plate 21 and the lower moving plate 19 are both bilaterally symmetrical with respect to the pin 8, the first lead screw 12 and the third lead screw 22 are bilaterally symmetrical, and the second lead screw 16 and the fourth lead screw 18 are bilaterally symmetrical.

In embodiment 4, in addition to embodiment 2, the right side of the upper moving plate 21 is screwed with a third screw 22, the right side of the lower moving plate 19 is screwed with a fourth screw 18, the third screw 22 is coaxially connected with the fourth screw 18 and has opposite screwing directions, and a synchronous transmission mechanism is provided between the first screw 12 and the third screw 22 or/and between the second screw 16 and the fourth screw 18. Namely, a synchronous motor is omitted compared with the embodiment 3, and two groups of screw rods are driven through a synchronous transmission mechanism.

The synchronous rotating mechanism comprises belt wheels which are respectively arranged on the first screw rod 12 and the third screw rod 22 or/and the second screw rod 16 and the fourth screw rod 22, and the left belt wheel and the right belt wheel are connected through a transmission belt.

The synchronous rotating mechanism comprises chain wheels 23 which are respectively arranged on the first screw rod 12 and the third screw rod 22 or/and the second screw rod 16 and the fourth screw rod 22, and the left belt wheel and the right belt wheel which are opposite are connected through a transmission chain 11.

Embodiment 5, a friction stir spot welding device, on the basis of any of the above embodiments, as shown in fig. 8 and 9, the driving mechanism and the transmission mechanism are both disposed in a housing 27, a housing cover 28 is detachably connected to the housing 27, the clamp ring 24 is connected to the housing cover 28 or/and the housing 27 and extends out of the housing cover 28, and an end of the lead screw is rotatably fitted with the clamp ring 24 through a bearing 17.

Spindle motor 1 and stirring cover power motor 2 set up at same height and all set up in quick-witted casing 27 through motor cabinet 29, axial driving motor 10 sets up in the casing 27 of spindle motor 1 top, and spindle motor 1, stirring cover power motor 2 and axial driving motor 10 all set up in quick-witted casing 27 through motor cabinet 29. The stirring pin 8 is connected with an output shaft of the spindle motor 1 through a sliding coupler 7, and the primary gear 5 is connected with the stirring sleeve power motor 2 through a gear driving shaft 4.

Example 6, a control method of a friction stir spot welding apparatus, as shown in fig. 1 to 7, includes a pressing stage, a stirring stage, a backfilling stage, and a demolding stage;

in the pressing stage, the working surfaces of the stirring pin 8, the stirring sleeve 9 and the pressing ring 24 are controlled to be in contact with the upper surface of the plate to be connected, and the pressing ring 24 is controlled to apply pressure downwards all the time;

in the stirring stage, a spindle motor 1 and an axial driving motor 10 are controlled to be started, the spindle motor 1 drives a stirring pin 8 to rotate, the axial driving motor 10 drives a screw rod to rotate forwards, the screw rod drives an upper moving plate 21 and a lower moving plate 19 to move synchronously, the stirring pin 8 is driven by the spindle motor 1 and the upper moving plate 21 to rotate and simultaneously gradually presses downwards, the stirring pin 8 is rubbed with an upper plate material of a plate material to be connected, the stirring sleeve 9 is driven by the lower moving plate 19 to move upwards while the stirring pin 8 presses downwards, a flowing space is provided for a material which is rubbed and melted by the stirring pin 8 and the plate material to be connected, and the space generated by the upward movement of the stirring sleeve 9 is gradually filled with the material which is rubbed and melted;

in the backfilling stage, after the stirring pin 8 is pressed downwards and stirred, the axial driving motor 10 is controlled to drive the screw rod to rotate reversely, the screw rod drives the upper moving plate 21 to move upwards to drive the stirring pin 8 to return upwards, the stirring pin 8 is withdrawn relative to a plate to be connected, meanwhile, the screw rod drives the lower moving plate 19 to move downwards to drive the stirring sleeve 9 to press downwards, meanwhile, the stirring sleeve 9 is driven by the stirring sleeve power motor 2 to rotate, the material which flows out in the stirring stage and is in a molten state is pressed back into a groove generated by the withdrawal of the stirring pin 8, and the groove generated by the stirring pin 8 is filled and leveled until the stirring pin 8, the stirring sleeve 9 and the compression ring 24 return to the initial positions;

Nothing in this specification is intended to be exhaustive of all conventional and well known techniques.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. The utility model provides a friction stir spot welding device, includes actuating mechanism, drive mechanism and friction stir mechanism, friction stir mechanism is including alternating complex stirring needle (8) and stirring cover (9), its characterized in that: friction stir mechanism includes with stirring cover (9) rotation fit's clamp ring (24), actuating mechanism includes spindle motor (1) and stirring cover motor power (2), drive mechanism includes one-level gear (5) that links to each other with stirring cover motor power (2), second gear (6) that link to each other with stirring cover (9), one-level gear (5) and second gear (6) meshing, circumference fixed connection and axial sliding fit between the output shaft of stirring needle (8) and spindle motor (1), stirring needle (8) circumference gyration is connected and axial fixedly connected with goes up movable plate (21), stirring cover (9) circumference gyration is connected and axial fixedly connected with moves movable plate (19) down, go up movable plate (21), move movable plate (19) down all with lead screw threaded connection down, lead screw and last movable plate (21) movable plate, The thread rotating directions of the matching of the lower moving plate (19) are opposite, the screw rod is connected with an axial driving motor (10), and the axial length of the meshing surface of the primary gear (5) and the secondary gear (6) is larger than the axial movement range of the upper moving plate (21).

2. The friction stir spot welding apparatus according to claim 1, wherein: the screw rod comprises a first screw rod (12) and a second screw rod (16) which are coaxially connected and have opposite thread turning directions, the upper moving plate (21) is in threaded connection with the first screw rod (12), the lower moving plate (19) is in threaded connection with the second screw rod (16), and the first screw rod (12) or the second screw rod (16) is connected with the axial driving motor (10).

3. The friction stir spot welding apparatus according to claim 2, wherein: the first screw rod (12) is in threaded connection with the left side of the upper moving plate (21), the second screw rod (16) is in threaded connection with the left side of the lower moving plate (19), the right side of the upper moving plate (21) is in threaded connection with a third screw rod (22), the right side of the lower moving plate (19) is in threaded connection with a fourth screw rod (18), the third screw rod (22) is in coaxial connection with the fourth screw rod (18), the thread turning directions are opposite, and the third screw rod (22) or the fourth screw rod (18) is connected with a motor synchronous with the axial driving motor (10).

4. The friction stir spot welding device according to claim 3, wherein: the upper moving plate (21) and the lower moving plate (19) are in bilateral symmetry with respect to the stirring needle (8), the first screw rod (12) and the third screw rod (22) are in bilateral symmetry, and the second screw rod (16) and the fourth screw rod (18) are in bilateral symmetry.

5. The friction stir spot welding apparatus according to claim 2, wherein: the right side of the upper moving plate (21) is in threaded connection with a third screw rod (22), the right side of the lower moving plate (19) is in threaded connection with a fourth screw rod (18), the third screw rod (22) is in coaxial connection with the fourth screw rod (18), the thread turning directions are opposite, and a synchronous transmission mechanism is arranged between the first screw rod (12) and the third screw rod (22) or/and between the second screw rod (16) and the fourth screw rod (18).

6. The friction stir spot welding apparatus according to claim 5, wherein: the synchronous rotating mechanism comprises belt wheels which are respectively arranged on the first screw rod (12) and the third screw rod (22) or/and the second screw rod (16) and the fourth screw rod (22), and the left belt wheel and the right belt wheel which are opposite are connected through a transmission belt.

7. The friction stir spot welding apparatus according to claim 5, wherein: the synchronous rotating mechanism comprises chain wheels (23) which are respectively arranged on the first screw rod (12) and the third screw rod (22) or/and the second screw rod (16) and the fourth screw rod (22), and the left belt wheel and the right belt wheel which are opposite are connected through a transmission chain (11).

8. The friction stir spot welding apparatus according to any one of claims 1 to 4 and 6 to 7, wherein: the driving mechanism and the transmission mechanism are both arranged in the machine shell (27), the machine shell (27) is detachably connected with a machine body cover (28), the pressing ring (24) is connected with the machine body cover (28) or/and the machine shell (27) and extends out of the machine body cover (28), and the end part of the screw rod is in rotary fit with the pressing ring (24) through a bearing (17).

9. The friction stir spot welding apparatus according to claim 8, wherein: spindle motor (1) and stirring cover motor power (2) set up at same height and all set up in quick-witted casing (27) through motor cabinet (29), axial driving motor (10) set up in casing (27) of spindle motor (1) top, link to each other through slip coupling (7) between the output shaft of stirring needle (8) and spindle motor (1), one-level gear (5) link to each other with stirring cover motor power (2) through gear drive axle (4).

10. The friction stir spot welding device control method according to any one of claims 1 to 9, characterized in that: comprises a compaction stage, a stirring stage, a backfill stage and a demoulding stage;

in the compaction stage, the working surfaces of the stirring needle (8), the stirring sleeve (9) and the compaction ring (24) are controlled to be in contact with the upper surface of the plate to be connected, and the compaction ring (24) is controlled to apply pressure downwards all the time;

in the stirring stage, a spindle motor (1) and an axial driving motor (10) are controlled to be started, the spindle motor (1) drives a stirring pin (8) to rotate, the axial driving motor (10) drives a screw rod to rotate forward, the screw rod drives an upper movable plate (21) and a lower movable plate (19) to move synchronously, the stirring pin (8) is driven by the spindle motor (1) and the upper movable plate (21) to rotate and simultaneously and gradually pressed downwards, the stirring pin (8) is rubbed with an upper plate material of a plate material to be connected, the stirring pin (8) is driven by the lower movable plate (19) to move upwards while being pressed downwards, a flowing space is provided for a material which is melted by friction between the stirring pin (8) and the plate material to be connected, and the space generated by moving upwards of the stirring pin (9) is gradually filled with the material which is melted by friction;

in the backfilling stage, after the stirring pin (8) is pressed downwards and stirred, the axial driving motor (10) is controlled to drive the screw rod to rotate reversely, the screw rod drives the upper moving plate (21) to move upwards to drive the stirring pin (8) to return upwards, the stirring pin (8) is withdrawn relative to the plate to be connected, meanwhile, the screw rod drives the lower moving plate (19) to move downwards to drive the stirring sleeve (9) to press downwards, meanwhile, the stirring sleeve (9) is driven by the stirring sleeve power motor (2) to rotate, the material in a molten state flowing out in the stirring stage is pressed back into the groove generated by withdrawing the stirring pin (8), the groove generated by the stirring pin (8) is filled up until the stirring pin (8), the stirring sleeve (9) and the compression ring (24) return to the initial positions;