Heavy load friction stir welding pin withdrawing device

Abstract

The application relates to a heavy-load friction stir welding pin withdrawing device, which is installed at the rear end of a heavy-load friction stir welding spindle (2), the front end of the heavy-load friction stir welding spindle (2) is provided with a heavy-load friction stir welding tool (3), the heavy-load friction stir welding tool (3) comprises a split structure of a pin (6) and a shoulder (5), the heavy-load friction stir welding pin withdrawing device comprises a rotary separation mechanism, a planetary screw servo driving mechanism and a pin withdrawing shaft (9), the planetary screw servo driving mechanism drives the pin withdrawing shaft (9) to continuously and stably withdraw the pin (6) into the shoulder (5) under the cooperation of the rotary separation mechanism. The heavy-load friction stir welding pin withdrawing device can eliminate the welding ring gap keyhole in the heavy-load friction stir welding forming process of a large-thickness high-strength aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of automated equipment technology for circumferential seam assembly and welding of fuel tank bodies for manned launch vehicles, and in particular to a heavy-duty friction stir welding stirring needle retraction device suitable for the assembly and welding of closed circumferential seams of thick, high-strength aluminum alloy tank bodies such as fuel tank bodies for manned launch vehicles. Background Technology

[0002] The welded area of ​​the fuel tank for my country's new-generation manned launch vehicle is over 22mm thick, with a total length of 40m. Using traditional fusion welding processes poses significant development risks. Currently, welding is one of the key technologies in rocket structure manufacturing within the aerospace industry. The application of welding processes and structures using thick, high-strength aluminum alloys such as 2219 aluminum alloy and 2195 aluminum-lithium alloy not only effectively improves the efficiency and reliability of launch vehicles but also greatly promotes the overall development of aerospace technology and enhances humanity's ability to explore outer space. To effectively utilize outer space resources, the development of various large launch vehicles has become a crucial foundation for the aerospace industry. Replacing the energy-intensive and polluting traditional fusion welding technology with advanced, efficient, and energy-saving friction stir welding green manufacturing technology to achieve efficient and lightweight manufacturing of aerospace structures has become a major trend in the development of large launch vehicles.

[0003] Friction stir welding (FSW) is a novel metal welding process that utilizes the high temperatures generated by the rotation and extrusion of a stirring head to induce plastic flow in the metal material near the stirring head, forming a dense microstructure at the joint of two workpieces, thus achieving the welding of metal parts. Compared to traditional welding processes, FSW offers advantages such as high joint quality, fewer defects, less deformation, lower labor intensity for workers, and a green and pollution-free welding process. Since rocket fuel tanks are special pressure vessels that need to stably and continuously supply the engine with the required fuel and oxidizer during rocket flight, the weld seams must maintain strict airtightness. Conventional FSW, due to the integrated needle and shoulder features of the stirring head, results in a keyhole at the weld end. Therefore, conventional FSW is often used for longitudinal seam welding, and the keyhole area is removed as a allowance after welding.

[0004] The friction stir welding of the circumferential seam of the launch vehicle fuel tank requires a retractable friction stir welding process capable of removing keyholes in the weld. This involves a separate structure for the stirring pin and the shoulder. After the friction stir welding spindle completes a full circumference weld, the stirring pin can be uniformly retracted along a certain length of the weld towards the shoulder to eliminate the keyhole. This retractable friction stir welding process places higher demands on the friction stir welding spindle equipment. First, the stirring head needs to withstand significant upsetting and forward resistance loads while simultaneously outputting high torque to meet the requirements of the material stirring welding process. Second, the stirring pin needs precise displacement servo control to achieve stable and continuous retraction under heavy load conditions. Due to space limitations of the friction stir welding spindle, the stirring pin retraction device needs to be highly integrated. Finally, the stirring pin retraction device must simultaneously rotate synchronously with the friction stir welding spindle to output stirring torque. Under significant upsetting force, the stirring pin must remain stably and reliably locked without retraction, and the stirring pin and shoulder must undergo linear relative motion under heavy load conditions to complete the retraction action. Summary of the Invention

[0005] The purpose of this invention is to provide an integrated motor servo drive and precise displacement control heavy-duty friction stir welding stirring pin retraction device, which ensures that the stirring pin rotates synchronously with the welding spindle during the friction stir welding of thick, high-strength aluminum alloys. At the same time, it is linked with the friction stir welding actuator to continuously and stably retract the stirring pin to eliminate the keyhole in the welding circumferential seam, thereby achieving high-quality, efficient, and reliable automated welding of thick, high-strength aluminum alloy tanks such as the fuel tank body of the next-generation manned launch vehicle.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a heavy-duty friction stir welding (FSM) needle retraction device, installed at the rear end of a heavy-duty FSM spindle, with a heavy-duty FSM stirring head installed at the front end of the spindle. The stirring head comprises a split-structure stirring needle and a shoulder. The spindle includes a spindle housing and a hollow motor installed within it. The hollow motor includes a rotor and a rotor shaft, with the rotor and shaft axially fixedly connected. The rotational torque output by the rotor to the rotor shaft is synchronously transmitted to the shoulder and the stirring needle, causing them to rotate synchronously. The retraction device includes a housing, a rotational separation mechanism and a planetary screw servo drive mechanism installed within the housing, and a retraction mechanism for the stirring needle. The stirring needle retraction shaft is located inside the hollow motor rotor shaft. Its front end extends out of the hollow motor rotor shaft and is inserted into the rear end of the shaft shoulder. Its rear end extends out of the hollow motor rotor shaft and is connected to the rotary separation mechanism. The rotary separation mechanism is connected to the planetary screw servo drive mechanism. The stirring needle is located inside the shaft shoulder, with its front end extending out of the shaft shoulder and its rear end inserted into the stirring needle retraction shaft from the front end and threadedly connected to it. The stirring needle has a degree of freedom to move along the axial centerline of the hollow motor rotor shaft within the shaft shoulder, referred to as the first degree of freedom. The stirring needle retraction shaft has a degree of freedom to move along the axial centerline of the hollow motor rotor shaft within the hollow motor rotor shaft, referred to as the second degree of freedom. The first and second degrees of freedom are the same. The planetary screw servo drive mechanism, in cooperation with the rotary separation mechanism, drives the stirring needle retraction shaft to move along the axial centerline of the hollow motor rotor shaft within the hollow motor rotor shaft, causing the stirring needle to retract inwards along the axial centerline of the hollow motor rotor shaft into the shaft shoulder.

[0008] Furthermore, the stirring pin retraction shaft is coaxial with the hollow motor rotor shaft; the stirring pin and the shaft shoulder are connected by a guide key to ensure that the stirring pin and the hollow motor rotor shaft are coaxial with the shaft centerline and that the stirring pin has the freedom to move along the axial centerline of the hollow motor rotor shaft within the shaft shoulder.

[0009] Furthermore, a guide bushing is provided for the stirring needle retraction shaft to move along the axial centerline of the hollow motor rotor shaft; the guide bushing for the stirring needle retraction shaft to move along the axial centerline of the hollow motor rotor shaft includes a first sliding bearing disposed inside the front part of the hollow motor rotor shaft and a second sliding bearing disposed inside the rear part of the hollow motor rotor shaft, the first sliding bearing and the second sliding bearing respectively contacting and connecting with the inner wall of the hollow motor rotor shaft and the outer wall of the stirring needle retraction shaft, and the first sliding bearing, the second sliding bearing and the hollow motor rotor shaft share the same axial centerline.

[0010] Furthermore, the heavy-duty friction stir welding head also includes a stirring head clamping handle. The rear end of the stirring head clamping handle is inserted into the hollow motor rotor shaft from the front end of the hollow motor rotor shaft and is connected to the hollow motor rotor shaft by screws to achieve axial fixation and is connected by a transmission key to achieve rotational torque transmission. The rear end of the shaft shoulder is inserted into the stirring head clamping handle from the front end of the stirring head clamping handle and is connected to the stirring head clamping handle by screws to achieve axial fixation and is connected by a transmission key to achieve rotational torque transmission.

[0011] Furthermore, the front end of the stirring needle retraction shaft is inserted into the shoulder sequentially from the rear end of the stirring head clamping handle and the rear end of the shoulder; the stirring needle retraction shaft is connected to the stirring head clamping handle through a first guide key, ensuring that the stirring needle retraction shaft and the hollow motor rotor shaft are aligned along the same axial centerline and that the stirring needle retraction shaft has the freedom to move along the axial centerline of the hollow motor rotor shaft within the stirring head clamping handle.

[0012] Furthermore, the rotary separation mechanism includes a first tapered roller bearing assembly, a guide shaft, a guide bushing, and a second tapered roller bearing assembly; the guide bushing is detachably and fixedly connected to the front interior of the heavy-duty friction stir welding agitator housing, and the front interior of the heavy-duty friction stir welding agitator housing is the guide bushing housing; the front end of the guide bushing housing is detachably and fixedly connected to the rear end of the heavy-duty friction stir welding main shaft housing, and a space is left between the guide bushing housing and the heavy-duty friction stir welding main shaft housing; the rear end of the guide bushing housing is connected to the rear end of the heavy-duty friction stir welding agitator housing. The front end of the device is detachably fixedly connected, and a space is left between the guide bushing housing and the rear part of the heavy-duty stirring friction welded stirring needle retraction device housing; the guide shaft and the hollow motor rotor shaft share the same axial centerline; the guide shaft has a degree of freedom to move along the axial centerline of the hollow motor rotor shaft within the guide bushing, referred to as the third degree of freedom; the third degree of freedom is consistent with the first degree of freedom; the rear end of the stirring needle retraction shaft is inserted into the guide shaft from the front end of the guide shaft; the front end of the guide shaft and the stirring needle retraction shaft are detachably fixedly connected by a first connecting piece; the stirring needle retraction shaft inside the guide shaft is connected to the guide shaft by a first tapered roller bearing assembly;

[0013] The planetary screw servo drive mechanism includes a retraction motor, a retraction planetary screw, and a retraction planetary screw nut. The retraction motor is installed inside the rear part of the housing of the heavy-duty friction stir welding stirring needle retraction device, and includes a retraction motor rotor and a retraction motor rotor shaft. The retraction planetary screw and the retraction motor rotor shaft share the same axial centerline. The front part of the retraction planetary screw is detachably and fixedly connected to the rear end of the guide shaft through a second connector, and the rear end is inserted into the retraction motor rotor shaft. The retraction planetary screw is threaded with a retraction planetary screw nut, which is located inside the retraction motor rotor shaft and detachably and fixedly connected to it. The retraction motor rotor shaft is axially fixedly connected to the retraction motor rotor, and the retraction motor rotor outputs rotational torque to the retraction motor rotor shaft, driving the retraction planetary screw nut to rotate.

[0014] The front part of the retraction motor rotor shaft is provided with a second tapered roller bearing assembly. The second tapered roller bearing assembly is in contact with the inner rear wall of the heavy-duty friction stir welding agitator housing and the outer front wall of the retraction motor rotor shaft, respectively. The rear part of the heavy-duty friction stir welding agitator housing is the retraction motor housing. The axial and radial positioning of the retraction motor rotor shaft is achieved by the second tapered roller bearing assembly, ensuring that the retraction motor rotor shaft and the hollow motor rotor shaft share the same axial centerline. At the same time, the second tapered roller bearing assembly bears the forging force of the agitator moving along the axial centerline of the hollow motor rotor shaft.

[0015] Furthermore, the front part of the retractable planetary screw is guided by a guide shaft and a guide bushing; the rear part of the retractable motor rotor shaft is provided with a retractable planetary screw guide needle roller bearing, which is in contact with the inner wall of the retractable motor rotor shaft and the outer wall of the retractable planetary screw respectively; the retractable planetary screw is guided in the retractable motor rotor shaft by the retractable planetary screw guide needle roller bearing, and the tolerance of the retractable planetary screw ensures that the retractable planetary screw has a degree of freedom to move along the axial centerline of the hollow motor rotor shaft in the retractable planetary screw guide needle roller bearing, which is called the fourth degree of freedom; the fourth degree of freedom is consistent with the first degree of freedom.

[0016] Furthermore, the guide shaft is located within the guide bushing and connected to the guide bushing via a second guide key, ensuring that the guide shaft and the hollow motor rotor shaft share the same axial centerline and that the guide shaft has the freedom to move within the guide bushing along the axial centerline of the hollow motor rotor shaft.

[0017] Furthermore, the retractable planetary screw and the second connecting member are connected by a retractable planetary screw flat key.

[0018] Furthermore, a set of cylindrical roller bearings is configured at the rear end of the retraction motor rotor shaft to bear radial loads and ensure that the retraction motor rotor shaft and the hollow motor rotor shaft are coaxially aligned.

[0019] Furthermore, the planetary screw servo drive mechanism also includes a retraction motor encoder; the retraction motor encoder is connected to the retraction motor rotor shaft through a corrugated coupling, and controls the rotational torque range of the retraction motor rotor shaft so that the degree of freedom of the retraction planetary screw moving along the axial center line of the hollow motor rotor shaft is consistent with the first degree of freedom, thereby precisely controlling the displacement of the stirring needle retracting into the shoulder along the axial center line of the hollow motor rotor shaft.

[0020] Furthermore, the retraction motor is a torque motor, and the planetary screw is a threaded roller screw.

[0021] Beneficial technical effects of the present invention:

[0022] The heavy-duty friction stir welding (FSM) needle retraction device of this invention fully utilizes the rear space of the heavy-duty FSM spindle housing, integrating the design of the heavy-duty FSM spindle. The retraction of the needle is driven by a servo torque motor combined with a planetary roller screw suitable for heavy-duty conditions, resulting in a compact size, fast response, and high load capacity. Bearings and motion guides ensure alignment of the rotation axis of the retraction motor rotor shaft, the motion axis of the planetary roller screw, and the rotation axis of the hollow motor rotor, ensuring high retraction accuracy and strong axial load capacity. A high-precision encoder enables semi-closed-loop control, guaranteeing servo accuracy of the needle retraction, resulting in fast response and high control precision. During the circumferential seam welding of the fuel tank, the needle retraction motion and the welding actuator's rotation around the seam are linked for continuous and stable retraction, eliminating keyholes in the weld seam. Under heavy-duty conditions, the retraction action is smooth and uninterrupted. The retraction force meets the requirements for retraction welding of 30mm thick aerospace high-strength aluminum alloys such as 2219 aluminum alloy and 2195 aluminum-lithium alloy, achieving high-quality, efficient, reliable, and automated welding of fuel tanks for next-generation manned launch vehicles. Attached Figure Description

[0023] Figure 1 A schematic diagram of the connection structure of the heavy-duty friction stir welding spindle slide box, the heavy-duty friction stir welding spindle, the heavy-duty friction stir welding stirring head and the heavy-duty friction stir welding stirring needle retraction device.

[0024] Figure 2 This is a perspective view of the heavy-duty friction stir welding stirring needle retraction device of the present invention;

[0025] Figure 3 This is a schematic diagram of the heavy-duty friction stir welding stirring needle retraction device of the present invention.

[0026] Figure 4 This is a schematic diagram of the rotary separation mechanism.

[0027] Figure 5 A schematic diagram of a planetary screw servo drive mechanism;

[0028] Figure 6This is a schematic diagram of the encoder structure for a retractable motor;

[0029] Figure 7 This is a schematic diagram of the retraction motor structure;

[0030] Figure 8 This is a comparison diagram of planetary screw and ball screw drives.

[0031] In the figure, 1-heavy-duty friction stir welding spindle slide box, 2-heavy-duty friction stir welding spindle, 3-heavy-duty friction stir welding stirring head, 4-heavy-duty friction stir welding stirring needle retraction device, 5-shoulder, 6-stirring needle, 7-first guide key, 8-first sliding bearing, 9-stirring needle retraction shaft, 10-second sliding bearing, 11-first tapered roller bearing assembly, 12-second guide key, 13-guide shaft, 14-guide bushing, 15-second tapered roller bearing assembly, 16-retraction planetary screw, 17-retraction motor rotor shaft, 18-retraction motor, 19-retraction planetary screw guide needle roller bearing, 20-cylindrical roller bearing, 21-retraction motor encoder, 22-retraction planetary screw key, 23-guide bushing housing, 24-retraction planetary screw nut, 25-retraction motor housing, 26-bellows coupling. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] In the description of this invention, it should be noted that the terms "front end", "rear end", "front part", "rear part", "external", "internal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0034] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be interpreted as indicating or implying relative importance.

[0035] See Figure 1-8This embodiment provides a heavy-duty friction stir welding stirring needle retraction device 4, installed at the rear end of a heavy-duty friction stir welding spindle 2. A heavy-duty friction stir welding stirring head 3 is installed at the front end of the spindle 2. The stirring head 3 includes a split-structure stirring needle 6 and a shoulder 5. The spindle 2 includes a spindle housing and a hollow motor installed within it. The hollow motor includes a rotor and a rotor shaft, with the rotor and rotor shaft axially fixedly connected. The rotational torque output by the rotor to the rotor shaft is synchronously transmitted to the shoulder 5 and the stirring needle 6, causing them to rotate synchronously. The heavy-duty friction stir welding stirring needle retraction device 4 includes a housing, a rotation separation mechanism and a planetary screw servo drive mechanism installed within the device, and a stirring needle retraction mechanism. Shaft 9; The stirring needle retraction shaft 9 is inside the hollow motor rotor shaft, with its front end extending out of the hollow motor rotor shaft and inserted into the rear end of the shaft shoulder 5, and its rear end extending out of the hollow motor rotor shaft and connected to the rotary separation mechanism; The rotary separation mechanism is connected to the planetary screw servo drive mechanism; The stirring needle 6 is inside the shaft shoulder 5, with its front end extending out of the shaft shoulder 5, and its rear end inserted into the stirring needle retraction shaft 9 from the front end and threadedly connected to the stirring needle retraction shaft 9; The stirring needle 6 has a degree of freedom to move along the axial centerline of the hollow motor rotor shaft within the shaft shoulder 5, referred to as the first degree of freedom; The stirring needle retraction shaft 9 has a degree of freedom to move along the axial centerline of the hollow motor rotor shaft within the hollow motor rotor shaft, referred to as the second degree of freedom; The first degree of freedom and the second degree of freedom are the same; The planetary screw servo drive mechanism, in cooperation with the rotary separation mechanism, drives the stirring needle retraction shaft 9 to move along the axial centerline of the hollow motor rotor shaft within the hollow motor rotor shaft, causing the stirring needle 6 to retract into the shaft shoulder 5 along the axial centerline of the hollow motor rotor shaft.

[0036] During the circumferential welding of the fuel tank body of the manned launch vehicle, the heavy-duty friction stir welding spindle 2 and the heavy-duty friction stir welding needle retraction device 4 are both installed in the heavy-duty friction stir welding spindle slide box 1 at the end of the circumferential welding actuator of the fuel tank body of the manned launch vehicle. The front end of the heavy-duty friction stir welding spindle 2 extends out of the heavy-duty friction stir welding spindle slide box 1, the heavy-duty friction stir welding stirring head 3 is installed at the front end of the heavy-duty friction stir welding spindle 2, and the heavy-duty friction stir welding needle retraction device 4 is installed at the rear end of the heavy-duty friction stir welding spindle 2.

[0037] In this embodiment, the stirring needle retraction shaft 9 and the hollow motor rotor shaft share the same axial centerline.

[0038] In this embodiment, the stirring pin 6 within the shoulder 5 is connected to the shoulder 5 via a guide key, ensuring that the stirring pin 6 shares a common axial centerline with the hollow motor rotor shaft and that the stirring pin 6 has the freedom to move within the shoulder 5 along the axial centerline of the hollow motor rotor shaft. The stirring pin retraction shaft 9 moves within the hollow motor rotor shaft along the axial centerline of the hollow motor rotor shaft, causing the stirring pin 6 to retract within the shoulder 5 along the axial centerline of the hollow motor rotor shaft.

[0039] In this embodiment, to ensure that the stirring needle retraction shaft 9 moves along the axial centerline of the hollow motor rotor shaft within the hollow motor rotor shaft, thereby driving the stirring needle 6 to move along the axial centerline of the hollow motor rotor shaft, a guide bushing is provided for the movement of the stirring needle retraction shaft 9 along the axial centerline of the hollow motor rotor shaft. The guide bushing includes a first sliding bearing 8 disposed inside the front part of the hollow motor rotor shaft and a second sliding bearing 10 disposed inside the rear part of the hollow motor rotor shaft. The first sliding bearing 8 and the second sliding bearing 10 are respectively in contact with the inner wall of the hollow motor rotor shaft and the outer wall of the stirring needle retraction shaft 9. The first sliding bearing 8, the second sliding bearing 10, and the hollow motor rotor shaft share a common axial centerline. The first sliding bearing 8 and the second sliding bearing 10 serve as the guide bushing for the movement of the stirring needle retraction shaft 9 along the axial centerline of the hollow motor rotor shaft, ensuring that the stirring needle retraction shaft 9 moves along the axial centerline of the hollow motor rotor shaft, thereby driving the stirring needle 6 to move along the axial centerline of the hollow motor rotor shaft.

[0040] In this embodiment, the heavy-duty friction stir welding head 3 further includes a stirring head clamping handle. The rear end of the stirring head clamping handle is inserted into the front end of the hollow motor rotor shaft and is axially fixed to the hollow motor rotor shaft by screws and transmitted rotational torque by a transmission key. The rear end of the shoulder 5 is inserted into the stirring head clamping handle and is axially fixed to the stirring head clamping handle by screws and transmitted rotational torque by a transmission key. The hollow motor rotor outputs rotational torque to the hollow motor rotor shaft, and the rotational torque is transmitted to the stirring head clamping handle through the transmission key, causing the stirring head clamping handle to rotate, thereby causing the shoulder 5 and the stirring needle 6 to rotate synchronously.

[0041] In this embodiment, the front end of the stirring needle retraction shaft 9 is inserted into the shoulder 5 sequentially from the rear end of the stirring head clamping handle and the rear end of the shoulder 5; the stirring needle retraction shaft 9 and the stirring head clamping handle are connected by the first guide key 7, ensuring that the stirring needle retraction shaft 9 and the hollow motor rotor shaft are aligned along the same axial centerline and that the stirring needle retraction shaft 9 has the freedom to move along the axial centerline of the hollow motor rotor shaft within the stirring head clamping handle.

[0042] In this embodiment, the rotary separation mechanism includes a first tapered roller bearing assembly 11, a guide shaft 13, a guide bushing 14, and a second tapered roller bearing assembly 15. The guide bushing 14 is detachably and fixedly connected to the interior of the front part of the heavy-duty friction stir welding agitator housing. The front part of the heavy-duty friction stir welding agitator housing is the guide bushing housing 23. The front end of the guide bushing housing 23 is detachably and fixedly connected to the rear end of the heavy-duty friction stir welding spindle housing, and a space is left between the guide bushing housing 23 and the heavy-duty friction stir welding spindle housing. The rear end of the guide bushing housing 23 is connected to the front end of the rear part of the heavy-duty friction stir welding agitator housing. The guide bushing housing 23 and the rear of the heavy-duty stirring friction welded stirring needle retraction device housing are detachably fixedly connected; the guide shaft 13 and the hollow motor rotor shaft share the same axial centerline; the guide shaft 13 has a degree of freedom to move along the axial centerline of the hollow motor rotor shaft within the guide bushing 14, referred to as the third degree of freedom; the third degree of freedom is consistent with the first degree of freedom; the rear end of the stirring needle retraction shaft 9 is inserted into the guide shaft 13 from the front end of the guide shaft 13; the front end of the guide shaft 13 and the stirring needle retraction shaft 9 are detachably fixedly connected by a first connecting member; the stirring needle retraction shaft 9 inside the guide shaft 13 is connected to the guide shaft 13 by a first tapered roller bearing assembly 11;

[0043] The planetary screw servo drive mechanism includes a retraction motor 18, a retraction planetary screw 16, and a retraction planetary screw nut 24. The retraction motor is installed inside the rear part of the housing of the heavy-duty stirring friction welding stirring needle retraction device, and includes a retraction motor rotor and a retraction motor rotor shaft 17. The retraction planetary screw 16 and the retraction motor rotor shaft 17 share the same axial centerline. The front part of the retraction planetary screw 16 is detachably and fixedly connected to the rear end of the guide shaft 13 through a second connector, and the rear end is inserted into the retraction motor rotor shaft 17. The retraction planetary screw nut 24 is threaded onto the retraction planetary screw 16, and the retraction planetary screw nut 24 is inside the retraction motor rotor shaft 17 and detachably and fixedly connected to the retraction motor rotor shaft 17. The retraction motor rotor shaft 17 is axially fixedly connected to the retraction motor rotor. The retraction motor rotor outputs rotational torque to the retraction motor rotor shaft 17, driving the retraction planetary wire nut 24 to rotate; the front part of the retraction motor rotor shaft 17 is provided with a second tapered roller bearing assembly 15, which is in contact with the inner rear wall of the heavy-duty stir friction welding stirring needle retraction device housing and the outer front wall of the retraction motor rotor shaft 17 respectively. The rear part of the heavy-duty stir friction welding stirring needle retraction device housing is the retraction motor housing 25; the axial and radial positioning of the retraction motor rotor shaft 17 is achieved through the second tapered roller bearing assembly 15, ensuring that the retraction motor rotor shaft 17 and the hollow motor rotor shaft share the same axial centerline, and at the same time, the second tapered roller bearing assembly 15 bears the forging force of the stirring needle 6 moving along the axial centerline of the hollow motor rotor shaft;

[0044] The first tapered roller bearing assembly 11, the guide shaft 13, and the second tapered roller bearing assembly 15 cooperate to separate the rotational motion of the stirring needle return shaft 9 while ensuring that it can withstand the forging force that causes the stirring needle return shaft 9 to move along the axial centerline of the hollow motor rotor shaft. In this way, the return planetary screw 16 moves along the axial centerline of the hollow motor rotor shaft under the rotation of the return planetary screw nut 24, which drives the guide shaft 13 to move along the axial centerline of the hollow motor rotor shaft within the guide bushing 14. This, in turn, drives the stirring needle return shaft 9 to move along the axial centerline of the hollow motor rotor shaft within the hollow motor rotor shaft, thus enabling the stirring needle 6 to move along the axial centerline of the hollow motor rotor shaft within the shoulder 5.

[0045] In this embodiment, the front part of the retractable planetary screw 16 is guided by the guide shaft 13 and the guide bushing 14; the rear part of the retractable motor rotor shaft 17 is provided with a retractable planetary screw guide needle roller bearing 19, which is in contact with the inner wall of the retractable motor rotor shaft 17 and the outer wall of the retractable planetary screw 16 respectively; the retractable planetary screw 16 is guided in the retractable motor rotor shaft 17 by the retractable planetary screw guide needle roller bearing 19, and the tolerance of the retractable planetary screw 16 ensures that the retractable planetary screw 16 has a degree of freedom to move along the axial centerline of the hollow motor rotor shaft in the retractable planetary screw guide needle roller bearing 19, which is called the fourth degree of freedom; the fourth degree of freedom is consistent with the first degree of freedom.

[0046] In this embodiment, the guide shaft 13 is inside the guide bushing 14 and connected to the guide bushing 14 via the second guide key 12, ensuring that the guide shaft 13 is coaxial with the hollow motor rotor shaft and that the guide shaft 13 has the freedom to move along the axial centerline of the hollow motor rotor shaft within the guide bushing 14.

[0047] In this embodiment, the retractable planetary screw 16 and the second connector are connected by a retractable planetary screw key 22.

[0048] In this embodiment, a set of cylindrical roller bearings 20 are configured at the rear end of the retraction motor rotor shaft 17 to bear radial loads, ensuring that the retraction motor rotor shaft 17 and the hollow motor rotor shaft are on the same axial centerline, resulting in high retraction accuracy and strong axial load bearing capacity.

[0049] In this embodiment, the planetary screw servo drive mechanism further includes a retraction motor encoder 21; the retraction motor encoder 21 is connected to the retraction motor rotor shaft 17 via a corrugated coupling 26, enabling precision transmission without backlash; the retraction motor encoder 21 is an integrated high-precision encoder that accurately measures the rotational torque of the retraction motor rotor shaft 17, thereby precisely controlling the rotational torque range of the retraction motor rotor shaft 17 so that the degree of freedom of the retraction planetary screw 16 moving along the axial centerline of the hollow motor rotor shaft is consistent with the first degree of freedom, thereby precisely controlling the displacement of the stirring needle 6 retracting into the shoulder 5 along the axial centerline of the hollow motor rotor shaft.

[0050] Furthermore, the retraction motor 18 is a torque motor, and the planetary screw 16 is a threaded roller screw. The planetary roller screw can withstand loads three times that of the planetary ball screw and has a lifespan 15 times that of the planetary ball screw.

[0051] The heavy-duty friction stir welding (FSM) needle retraction device in this embodiment fully utilizes the rear space of the heavy-duty FSM spindle housing. The integrated design of the heavy-duty FSM spindle, driven by a servo torque motor and a planetary roller screw suitable for heavy-duty conditions, results in a small size, fast response, and high load capacity. The planetary roller screw replaces the planetary ball screw, releasing the load through numerous contact points, significantly improving rigidity and impact resistance. Bearings and motion guides ensure alignment of the retraction motor rotor shaft rotation axis, the planetary roller screw motion axis, and the hollow motor rotor rotation axis, resulting in high retraction accuracy and strong axial load capacity. A high-precision grooving system is also included. The encoder achieves semi-closed-loop control to ensure the servo accuracy of the stirring pin retraction, with fast response and high control precision. It enables continuous and stable retraction of the stirring pin, eliminating keyholes in the weld seam during the friction stir welding process of manned launch vehicle fuel tanks. The stirring pin retraction shaft 9 has a working stroke of 60mm, a retraction positioning accuracy of 0.03mm, and a repeatability of 0.02mm. Under heavy load conditions, the retraction action is smooth and without jamming. The retraction force meets the requirements for retraction welding of 30mm thick aerospace high-strength aluminum alloys such as 2219 aluminum alloy and 2195 aluminum-lithium alloy, realizing high-quality, efficient, reliable, and automated welding of the next-generation manned launch vehicle fuel tank.

[0052] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A heavy-duty friction stir welding stirring needle retraction device, installed at the rear end of a heavy-duty friction stir welding spindle (2), wherein a heavy-duty friction stir welding stirring head (3) is installed at the front end of the friction stir welding spindle (2); characterized in that, The heavy-duty friction stir welding stirring head (3) includes a split-structure stirring needle (6) and a shoulder (5); the heavy-duty friction stir welding spindle (2) includes a hollow motor; the hollow motor includes a hollow motor rotor and a hollow motor rotor shaft, the hollow motor rotor and the hollow motor rotor shaft are axially fixedly connected, the rotational torque output by the hollow motor rotor to the hollow motor rotor shaft is synchronously transmitted to the shoulder (5) and the stirring needle (6), driving the shoulder (5) and the stirring needle (6) to rotate synchronously; the heavy-duty friction stir welding stirring needle retraction device includes a rotation separation mechanism and a planetary screw servo drive mechanism, as well as a stirring needle retraction shaft (9); the stirring needle retraction shaft (9) is inside the hollow motor rotor shaft, the front end extends out of the hollow motor rotor shaft and is inserted into the shoulder (5) from the rear end of the shoulder (5), the rear end extends out of the hollow motor rotor shaft and is connected to the rotation separation mechanism; the rotation The rotary separation mechanism is connected to the planetary screw servo drive mechanism; the stirring needle (6) is inside the shoulder (5), with its front end extending out of the shoulder (5) and its rear end inserted into the stirring needle retraction shaft (9) from the front end and threadedly connected to the stirring needle retraction shaft (9); the stirring needle (6) has a degree of freedom to move along the axial center line of the hollow motor rotor shaft inside the shoulder (5), which is called the first degree of freedom; the stirring needle retraction shaft (9) has a degree of freedom to move along the axial center line of the hollow motor rotor shaft inside the hollow motor rotor shaft, which is called the second degree of freedom; the first degree of freedom is consistent with the second degree of freedom; the planetary screw servo drive mechanism, in cooperation with the rotary separation mechanism, drives the stirring needle retraction shaft (9) to move along the axial center line of the hollow motor rotor shaft inside the hollow motor rotor shaft, thereby driving the stirring needle (6) to retract into the shoulder (5) along the axial center line of the hollow motor rotor shaft; The rotating separation mechanism includes a first tapered roller bearing assembly (11), a guide shaft (13), a guide bushing (14), and a second tapered roller bearing assembly (15); the guide shaft (13) is coaxial with the hollow motor rotor shaft; the guide shaft (13) has a degree of freedom to move within the guide bushing (14) along the axial centerline of the hollow motor rotor shaft, which is called the third degree of freedom; the third degree of freedom is consistent with the first degree of freedom; the rear end of the stirring needle retraction shaft (9) is inserted into the guide shaft (13) from the front end of the guide shaft (13); The front end of the guide shaft (13) is detachably and fixedly connected to the stirring needle retraction shaft (9) via a first connector; the stirring needle retraction shaft (9) inside the guide shaft (13) is connected to the guide shaft (13) via a first tapered roller bearing assembly (11); the planetary screw servo drive mechanism includes a retraction motor (18), a retraction planetary screw (16), and a retraction planetary screw nut (24), the retraction motor (18) includes a retraction motor rotor and a retraction motor rotor shaft (17); the retraction planetary screw (16) and the retraction motor rotor shaft (17) Coaxial centerline; the front part of the retracting planetary screw (16) is detachably and fixedly connected to the rear end of the guide shaft (13) through a second connector, and the rear end is inserted into the retracting motor rotor shaft (17); the retracting planetary screw (16) is threaded with a retracting planetary screw nut (24), the retracting planetary screw nut (24) is inside the retracting motor rotor shaft (17) and is detachably and fixedly connected to the retracting motor rotor shaft (17); the retracting motor rotor shaft (17) is axially fixedly connected to the retracting motor rotor, and the retracting motor rotor is retracting... The rotary torque output by the rotary motor rotor shaft (17) drives the rotary planetary screw nut (24) to rotate; the front part of the rotary motor rotor shaft (17) is provided with a second tapered roller bearing assembly (15), which realizes the axial and radial positioning of the rotary motor rotor shaft (17) through the second tapered roller bearing assembly (15), ensuring that the rotary motor rotor shaft (17) and the hollow motor rotor shaft share the same axial center line, and at the same time, the second tapered roller bearing assembly (15) bears the forging force of the stirring needle (6) moving along the axial center line of the hollow motor rotor shaft; The rear interior of the retractable motor rotor shaft (17) is provided with a retractable planetary screw guide needle roller bearing (19), which is in contact with the inner wall of the retractable motor rotor shaft (17) and the outer wall of the retractable planetary screw (16). The retractable planetary screw (16) is guided within the retractable motor rotor shaft (17) by the retractable planetary screw guide needle roller bearing (19). The tolerance of the retractable planetary screw (16) ensures that the retractable planetary screw (16) has a degree of freedom to move along the axial centerline of the hollow motor rotor shaft within the retractable planetary screw guide needle roller bearing (19), which is called the fourth degree of freedom. The fourth degree of freedom is consistent with the first degree of freedom.

2. The heavy-duty friction stir welding stirring pin retraction device according to claim 1, characterized in that, The stirring needle retraction shaft (9) is coaxial with the hollow motor rotor shaft; the stirring needle (6) in the shoulder (5) is connected to the shoulder (5) by a guide key to ensure that the stirring needle (6) is coaxial with the hollow motor rotor shaft and that the stirring needle (6) has the freedom to move along the axial centerline of the hollow motor rotor shaft in the shoulder (5).

3. The heavy-duty friction stir welding stirring pin retraction device according to claim 1, characterized in that, The guide bushing for moving the stirring needle retraction shaft (9) along the axial centerline of the hollow motor rotor shaft includes a first sliding bearing (8) disposed inside the front part of the hollow motor rotor shaft and a second sliding bearing (10) disposed inside the rear part of the hollow motor rotor shaft. The first sliding bearing (8) and the second sliding bearing (10) are respectively in contact with the inner wall of the hollow motor rotor shaft and the outer wall of the stirring needle retraction shaft (9). The first sliding bearing (8), the second sliding bearing (10) and the hollow motor rotor shaft share the same axial centerline.

4. The heavy-duty friction stir welding stirring pin retraction device according to claim 1, characterized in that, The heavy-duty friction stir welding stirring head (3) also includes a stirring head clamping handle. The rear end of the stirring head clamping handle is inserted into the hollow motor rotor shaft from the front end of the hollow motor rotor shaft and is connected to the hollow motor rotor shaft by screws to achieve axial fixation and to achieve rotational torque transmission by transmission key. The rear end of the shoulder (5) is inserted into the stirring head clamping handle from the front end of the stirring head clamping handle and is connected to the stirring head clamping handle by screws to achieve axial fixation and to achieve rotational torque transmission by transmission key.

5. The heavy-duty friction stir welding stirring pin retraction device according to claim 4, characterized in that, The front end of the stirring needle retraction shaft (9) is inserted into the rear end of the stirring head clamping handle and the rear end of the shoulder (5) in sequence; the stirring needle retraction shaft (9) is connected to the stirring head clamping handle through the first guide key (7) to ensure that the stirring needle retraction shaft (9) and the hollow motor rotor shaft are aligned along the same axial center line and that the stirring needle retraction shaft (9) has the freedom to move along the axial center line of the hollow motor rotor shaft within the stirring head clamping handle.

6. The heavy-duty friction stir welding stirring pin retraction device according to claim 1, characterized in that, The guide shaft (13) is inside the guide bushing (14) and connected to the guide bushing (14) via the second guide key (12), ensuring that the guide shaft (13) and the hollow motor rotor shaft are aligned along the same axial centerline and that the guide shaft (13) has the freedom to move along the axial centerline of the hollow motor rotor shaft within the guide bushing (14).

7. The heavy-duty friction stir welding stirring pin retraction device according to claim 1, characterized in that, The retractable planetary screw (16) is connected to the second connector via a retractable planetary screw key (22).

8. The heavy-duty friction stir welding stirring pin retraction device according to claim 1, characterized in that, The planetary screw servo drive mechanism also includes a retraction motor encoder (21); the retraction motor encoder (21) is connected to the retraction motor rotor shaft (17) through a corrugated coupling (26), and controls the rotational torque range of the retraction motor rotor shaft (17) so that the degree of freedom of the retraction planetary screw (16) moving along the axial centerline of the hollow motor rotor shaft is consistent with the first degree of freedom.

9. The heavy-duty friction stir welding stirring pin retraction device according to claim 1, characterized in that, The rear end of the retraction motor rotor shaft (17) is equipped with a set of cylindrical roller bearings (20) to bear radial loads and ensure that the retraction motor rotor shaft (17) and the hollow motor rotor shaft are on the same axial center line.

10. The heavy-duty friction stir welding stirring pin retraction device according to claim 1, characterized in that, The retraction motor is a torque motor, and the retraction planetary screw (16) is a threaded roller screw.

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