CN114985539A

CN114985539A - Variable-diameter core rod for bending forming of aerospace ultrathin-wall pipe

Info

Publication number: CN114985539A
Application number: CN202210729042.3A
Authority: CN
Inventors: 蒋兰芳; 潘浩; 李威; 高逸翔; 杨铭
Original assignee: Zhejiang University of Technology ZJUT
Current assignee: Zhejiang University of Technology ZJUT
Priority date: 2022-06-24
Filing date: 2022-06-24
Publication date: 2022-09-02

Abstract

The invention discloses a variable-diameter core rod for bending and forming an aerospace ultrathin-wall pipe. The variable-diameter core ball chain is formed by assembling a plurality of variable-diameter core balls in a matched manner through a ball hinge; the middle main body of the variable-diameter core ball is provided with a servo motor driving large pin gear, the large pin gear transmits motion to a plurality of small pin gears, the small pin gears are arranged on a plurality of threaded transmission shafts, the threaded transmission shafts rotate to drive the middle connecting slide block to do linear motion in the radial direction to realize the diameter-changing function, and the rear end of the middle connecting slide block is provided with a support rod and an arc support block to realize the support of the spherical surface. The tail part of the core ball is provided with an adjusting locking mechanism, the adjusting handle realizes the opening and closing of the middle spherical cavity through the movement of the notch, and the spherical hinge matching of a plurality of core balls is realized. The invention has simple structure and convenient diameter adjusting range, can reduce the cost in the forming of the aviation elbow and improve the production efficiency.

Description

Variable-diameter core rod for bending forming of aerospace ultrathin-wall pipe

Technical Field

The invention relates to the field of pipe bending forming, in particular to a variable-diameter core rod for bending forming of an aerospace ultrathin-wall pipe.

Background

At present, the bent pipe technology is widely applied in the fields of aviation and automobile manufacturing, and the improvement of the bent pipe forming quality plays an important role in improving the production efficiency. However, since the tube is hollow, the tube can be bent by being directly placed in a tube bending machine, which causes various defects of the tube, including: the bend has wrinkling, collapse, cross-sectional distortion, etc. In order not to affect the quality of the pipe bending, it is common to avoid the above-mentioned drawbacks by placing a mandrel as a support in the pipe. However, during the production process, for pipes of different diameters, a series of mandrels of different diameters is often required as support, which results in a large stockpile of mandrels. In order to solve the above problems, a supporting core rod capable of continuously changing different diameters needs to be designed to adapt to pipes with different diameters.

Disclosure of Invention

Aiming at the problems brought forward in the background, the core rod capable of continuously realizing diameter change is provided, meanwhile, the core rod and the core ball chain, and the core balls can be freely assembled, the adjustment is convenient, and the production cost can be reduced.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a variable-diameter core rod for bending and forming an aerospace ultrathin-wall pipe comprises a core rod and a variable-diameter core ball chain; the variable-diameter core ball chain is formed by matching a plurality of variable-diameter core balls through ball hinges;

the core rod comprises a core rod upper top cover, a core rod main body, a first cam disc, a first locking block, a second cam disc and a first adjusting handle; the upper top cover is fixedly connected to the core rod main body; the core rod locking mechanical mechanism assembled by the cam disc I, the locking block I and the cam disc II is positioned in the upper top cover; the cam disc II is fixedly connected to the core rod main body; the first cam disc and the second cam disc are respectively provided with a plurality of notches I and II; the upper surface and the lower surface of the first locking block are respectively provided with a first guide pillar and a second guide pillar, and the first locking block is opened and closed by matching the first guide pillar with the first notch and matching the second guide pillar with the second notch; the first adjusting handle is assembled on the first cam disc and used for adjusting the opening and closing of the first locking block;

the variable-diameter core ball comprises a main body supporting part, a core ball diameter adjusting part and an adjusting and locking part; the ball body of the diameter-variable core ball is embedded into a core rod locking mechanical mechanism of the core rod, diameter variation is realized through the core ball diameter adjusting part, and spherical hinge matched locking of the diameter-variable core ball is realized through the adjusting locking part.

Furthermore, the main body supporting part comprises an upper mounting cover, a middle cavity, an arc supporting block, a supporting rod, a middle section connecting slide block and a motor mounting plate;

the upper mounting cover is fixedly connected with the middle cavity; the arc supporting blocks are uniformly arranged around the middle cavity; each arc supporting block is fixedly connected with the middle section connecting sliding block through two supporting rods; the motor mounting plate is arranged on the middle cavity.

Furthermore, the core ball diameter adjusting part comprises a threaded transmission shaft, a motor, a small pin gear, a large pin gear, a coupler, a driving shaft, a ball bearing and a bearing seat;

the number of the threaded transmission shafts is equal to that of the middle connecting sliding blocks, and the threaded transmission shafts and the middle connecting sliding blocks are connected in a threaded fit mode; the shaft head of the threaded transmission shaft is fixedly connected with a small pin gear; the motor is arranged on the motor mounting plate and is connected with the driving shaft through a coupler, and the driving shaft is fixedly connected with the large pin gear; the ball bearing is connected with the bearing seat in an interference fit manner; the bearing block is fixedly connected to the middle cavity; the threaded transmission shaft is supported on the middle cavity through the ball bearing; the threaded transmission shaft is in threaded connection with the middle section connecting slide block;

the motor drives the driving shaft to rotate so as to drive the large pin gear to rotate; the large pin gear transmits rotary motion to the small pin gear through gear matching, the small pin gear rotates through driving the transmission shaft, the transmission shaft drives the middle section connecting slide block to slide through thread transmission, the arc supporting block is further driven to do radial linear motion, and reducing is achieved.

Furthermore, the adjusting and locking part comprises a lower mounting cover, an adjusting handle II, a cam disc III, a locking block II, a cam disc IV and a support column II;

the lower mounting cover is fixedly connected to the middle cavity; a core ball locking mechanical mechanism consisting of the cam disc IV, the locking block II and the cam disc III is positioned between the lower mounting cover and the mounting groove II of the middle cavity; the locking block II is provided with a plurality of notches I, a plurality of notches II are formed in the locking block II, a plurality of locking blocks II are arranged on the upper surface and the lower surface of the locking block II, and the locking block II is opened and closed through the matching of the locking block II and the locking block II; and the adjusting handle II is assembled on the cam disc III and used for adjusting the opening and closing of the locking block II.

Furthermore, the number of the arc supporting blocks is six; six middle section connecting slide blocks are provided, and twelve supporting rods are provided.

The invention has the following beneficial effects:

(1) the invention adopts a threaded transmission shaft as a reducing mechanism, and two supporting blocks and an arc supporting block as supporting mechanisms. But the screw thread transmission shaft and the two support rods are arranged up and down on the slide block in space, so that the movement stroke of the screw thread transmission shaft is large, the diameter-variable range of the core ball is large, and the diameter-variable range of more than 1.3D can be realized.

(2) The mechanical mechanisms are arranged at the tail part of the core ball and the top part of the core rod and are used as adjusting and locking mechanisms, the size is small, the adjustment is convenient, the assembly and disassembly can be completed only by adjusting the handle, the problem that the assembly can only be carried out but cannot be disassembled in the traditional production is avoided, the flexible assembly of the number of the core ball chains is realized, various requirements of pipes with different lengths on the number of the core balls can be met, and the utilization rate is improved.

(3) The motor is used as power drive, the thread transmission shaft is used as a main transmission mechanism, and the self-locking between the motor control and the screw pair can be realized, so that the large load can be borne, the support block can not slide in the radial direction due to the applied external load in the pipe bending process, and the precision is improved.

Drawings

FIG. 1 is a schematic view of the overall structure of a variable-diameter core rod for bending and forming an aerospace ultra-thin wall pipe;

fig. 2 is a schematic view of the structure of the whole variable-diameter core baseball shown in fig. 1;

FIG. 3 is a schematic view of the mandrel configuration of FIG. 1;

FIG. 4 is an exploded view of the mandrel of FIG. 1 and an enlarged view of a portion of the part;

FIG. 5 is a schematic view of the movement of the locking structure of FIG. 2;

FIG. 6 is a schematic structural view of the variable diameter core ball of FIG. 2;

FIG. 7 is a schematic view of a portion of the construction of the variable diameter core ball of FIG. 3;

FIG. 8 is a schematic structural view of the variable diameter core ball of FIG. 3;

FIG. 9 is a schematic diagram of a portion of the structure of the variable diameter core ball of FIG. 3;

FIG. 10 is a schematic detail view of the intermediate connecting slide 35 of FIG. 3;

FIG. 11 is a schematic view of the intermediate chamber 32 of FIG. 3 with parts broken away

Fig. 12 is a schematic view of the range of variation in fig. 3.

In the figure, a mandrel 1, a variable-diameter mandrel ball 2, a main body supporting part 3, a mandrel ball diameter adjusting part 4, an adjusting locking part 5, a mandrel upper top cover 11, a mandrel main body 12, a cam disc 13, a locking block 14, a lower cam disc 15, an adjusting handle 16, a mounting groove 121, a threaded hole 131, a groove 132, a guide pillar 141, a guide pillar 142, a groove 151, an upper mounting cover 31, a middle cavity 32, a circular arc supporting block 33, a supporting rod 34, a middle section connecting slide block 35, a motor mounting plate 36, a through hole 321, a mounting groove 322, a mounting groove three 323, a threaded through hole 351, a threaded transmission shaft 41, a motor 42, a small pin gear 43, a large pin gear 44, a coupling 45, a driving shaft 46, a ball bearing 47, a bearing seat 48, a threaded section 411, a lower mounting cover 51, an adjusting handle 52, a cam disc three 53, a locking block two 54, a cam disc four 55, a threaded hole two 531, notch three 532, guide pillar three 541, guide pillar four 542, notch four 551.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the objects and effects of the present invention will become more apparent, and the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.

As shown in fig. 1-12, the variable-diameter mandrel for bending and forming an aerospace ultra-thin wall pipe comprises a mandrel 1 and a variable-diameter mandrel ball chain. The variable-diameter core ball chain is formed by matching a plurality of variable-diameter core balls 2 through a ball hinge, and each variable-diameter core ball 2 comprises a main body supporting part 3, a core ball diameter adjusting part 4 and an adjusting and locking part 5.

As shown in FIG. 4, the mandrel 1 comprises a mandrel upper cover 11, a mandrel main body 12, a cam plate I13, ten locking blocks I14, a cam plate II 15 and an adjusting handle I16. Wherein, the mandrel main body 12 is provided with a first mounting groove 121; the first cam disc 13 is provided with a first threaded hole 131 and a first ten notches 132; the first locking block 14 is provided with a first guide post 141 and a second guide post 142; the second cam disc 15 is provided with a second notch 151.

The upper top cover 11 and the main body 12 of the core rod are assembled through screws; the cam disc I13, the ten locking blocks I14 and the lower cam disc 15 are assembled into the lower cam disc 15 of the locking mechanism, and the lower cam disc 15 is installed on the mandrel main body 12 through screws. The mandrel main body 12 is provided with a first mounting groove 121, and the cam disc II 15 is mounted in the first mounting groove 121 through a screw; the first locking block 14 comprises a first guide post 141 and a second guide post 142, after the second cam disc 15 is installed, the second guide post 142 is installed in a second notch 151 formed in the second cam disc 15, and ten first locking blocks 14 are installed in sequence; after ten locking blocks 14 are installed on the cam plate I13, the notch I132 is installed in alignment with the guide posts I141; the first cam plate is provided with a first threaded hole 131, and the first handle 16 is screwed on the first cam plate 13.

The adjustment locking movement on the integral mandrel 1 is as follows: the first adjusting handle 16 rotates with the rotation of the human hand to drive the first cam disc 13 to rotate, the first notch 132 on the first adjusting handle drives the first guide post 141 to rotate, and meanwhile, the second guide post on the locking block 14 is assembled with the second notch 151 on the second cam disc 15 to limit the second guide post to move linearly along the second notch 151, and when the second guide post 142 moves to the farthest end of the second notch 151, ten locking blocks 14 are in a fully opened state, as shown in fig. 5. The central area of the integral locking block I14, the cam disc II 15 and the core rod main body 12 at the locking position is cut into a sphere shape, so that the opening and closing of the spherical cavity on the space can be realized by adjusting the position of the parts in the space by using the adjusting handle I16. When ten locking blocks 14 are completely opened, the ball head of the next variable-diameter core ball 2 is placed in, and after the first handle 16 is adjusted, the mechanism is locked, so that the spherical hinge matching of the core rod 1 and the variable-diameter core ball chain is completed.

As shown in fig. 6 and 7, the main body support portion 3 includes an upper mounting cover 31, a middle cavity 32, six arc support blocks 33, twelve support rods 34, six middle section connection sliders 35, and a motor mounting plate 36. As shown in fig. 11, the middle chamber 32 has six through holes 321, two mounting grooves 322 and three mounting grooves 323. The middle section connecting slide block 35 is provided with a first threaded through hole 351. The upper mounting cap 31 is connected to the intermediate chamber 32 by a pin. The arc supporting block 33 is connected with the two supporting rods 34 through threads; the middle section connecting slide block 35 is connected with the two support rods 34 through threads; the motor mounting plate 36 is mounted on the intermediate cavity 32 by a screw connection.

As shown in fig. 7 and 9, the core ball diameter adjusting section 4 includes six threaded transmission shafts 41, a motor 42, six small pin gears 43, a large pin gear 44, a coupling 45, a drive shaft 46, six ball bearings 47, and six bearing seats 48. Wherein the threaded transmission shaft 41 is provided with a first threaded section 411.

As shown in fig. 7, the motor 42 is mounted on the motor mounting plate 36 by screw connection. As shown in fig. 9, both ends of the coupling 45 are respectively engaged with the motor 42 and the driving shaft 46; the driving shaft 46 is connected with the large pin gear 44 through a flat key; the large pin gear 44 and the small pin gear 43 transmit motion through gear matching; the small pin gear 43 is connected with the threaded transmission shaft 41 through a flat key; one section of the threaded transmission shaft 41 passes through the first through hole 321 of the middle cavity 32 and is provided with a first threaded section 411, the middle section connecting slide block 35 is provided with a first threaded through hole 351, and the two are connected through threads to install the middle section connecting slide block 35 on the threaded transmission shaft 41. The middle section connecting slide block 35 is fixedly connected with the arc supporting block 33 through two supporting rods 34, and plays a role in supporting the bent pipe. As shown in fig. 8, the bearing seat 48 is mounted on the mounting groove three 323 of the middle cavity 32 by screws; the ball bearing 47 is mounted on a bearing block 48, where the bearing functions to support the rotating shaft and parts on the shaft and to maintain the normal operating position and rotational accuracy of the shaft.

As shown in fig. 9, the core ball diameter adjusting portion operates on the following principle: after the motor 42 is started, it will drive the motor shaft to rotate, the coupling 45 assembled with the motor shaft will also rotate together, and the transmission shaft 46 assembled with the coupling 45 and the large pin gear 44 assembled with the transmission shaft 46 will both rotate. The large pin gear 44 transfers the rotational motion to the small pin gear 43 through the gear engagement, and in turn, because the small pin gear 43 is connected to the driving screw shaft 41 through the flat key to make the rotational motion. The middle section connecting slide block 35 is connected with the threaded transmission shaft 41 through threads, the middle section connecting slide block 35 is assembled on the threaded transmission shaft 41 to do linear motion, the direction is in the radial direction of the variable-diameter core ball, the arc supporting block 33 is connected to the middle section connecting slide block 35 through the supporting rod 34 serving as a connecting piece, and the arc supporting block 33 also does radial linear motion on the variable-diameter core ball, so that variable-diameter support can be realized.

As shown in fig. 9, in terms of spatial layout, the threaded transmission shaft 41 is fixed in the middle of the intermediate connection slider 35, the support rods 34 are distributed above and below the intermediate connection slider 35, and meanwhile, in the radial direction, when the variable-diameter core ball 2 is at the minimum radius position, the intermediate connection slider 35 is located at the position closest to the center of the core ball, with the rotation of the threaded transmission shaft 41, the support rods 34 and the arc support blocks 33 move in the direction away from the center of the core ball, and the intermediate connection slider 35 gradually moves to the outermost position of the threaded transmission shaft 41, thereby completing the movement of reducing diameter. As shown in fig. 12, at the minimum radius position, the whole position of the threaded transmission shaft 41 is located below the support rod 34, and the radius of the whole variable-diameter core ball 2 is determined mainly according to the length of the support rod 34; but moving to the position with the largest radius, the radius of the whole variable-diameter core ball 2 is determined by the length of the supporting rod 34 and the thread length of the threaded transmission shaft 41, and a larger adjusting range can be realized on the radius range, and the radius is changed from R to R of 1.31. The arc supporting block 33 is prevented from slipping under the action of external load, a motor with a small size and an electromagnetic band-type brake can be selected, and meanwhile, a thread with a lead angle smaller than a friction angle is machined on the thread transmission shaft 41, so that the quality of bent pipes cannot be guaranteed due to the fact that the radius is changed under the action of the external load in the pipe bending process.

The adjusting and locking part 5 comprises a lower mounting cover 51, a second adjusting handle 52, a third cam disc 53, a second locking block 54 and a fourth cam disc 55. The cam plate III 53 is provided with a threaded hole II 531 and ten notches III 532; the second locking block 54 is provided with a third guide pillar 541 and a fourth guide pillar 542; the cam plate four 55 is provided with ten notches four 551. The lower mounting cover 51 and the intermediate cavity 32 are assembled by screws; the middle cavity 32 is provided with a second mounting groove 322, and the cam disc IV 55 is mounted in the second mounting groove 322 through a screw; the second locking block 54 comprises a third guide post 541 and a fourth guide post 542, and after the fourth cam plate 55 is installed, the fourth guide post 542 is installed in a fourth notch 551 arranged on the fourth cam plate 55, and ten second locking blocks 54 are installed in sequence. After the ten locking blocks two 54 are installed, the cam plate three 53 is installed by aligning the notch three 532 with the ten guide posts three 541; the cam plate three 53 is provided with a threaded hole two 531, and the adjusting handle two 52 is screwed on the cam plate three 53. Meanwhile, the cam disc III 53 is provided with three pin holes, so that the cam disc III 53 is limited to a fixed position during locking through pin connection, and the falling-off phenomenon caused by the mutual movement between the cam disc III and the cam disc III in the spherical hinge fit can be prevented.

The following is the installation process of the variable-diameter core rod for bending and forming the aerospace ultrathin-wall pipe.

First, the variable diameter core ball 2 is separately installed. As shown in fig. 9, the core ball diameter adjusting section 4 is assembled first. Firstly, a motor 42, a coupler 45 and a large pin gear 44 are installed together, and then the middle connecting slide block 35 and the threaded transmission shaft 41 are installed together through threads; a bearing seat 48 and a ball bearing 47 are respectively arranged on the mounting groove III 323 of the middle cavity 32; assembling the unthreaded section of the threaded transmission shaft 41 with the small pin gear 43 through the first through hole 321 on the middle cavity 32, repeating the steps for six times, installing the six directions, then adjusting the large pin gear 44 and the small pin gear 43 to complete the matching between the pin gears, and finally installing the motor on the motor installation plate 36 by using screws.

Then, the mounting of the main body support portion 3 is performed. As shown in fig. 9, two support rods 34 are installed in two threaded holes of the middle connecting slider 35, and then the arc support blocks 35 are installed at the other two ends of the two support rods 34; the upper mounting cap 31 is then assembled to the intermediate cavity by means of pins.

Adjustment of the mounting of the locking portion 5 is then performed. The four cam plates 55 are arranged on the two mounting grooves 322 of the middle cavity 32 by screws, the four guide posts 542 of the ten locking blocks 54 are arranged on the corresponding ten notches 551 of the four cam plates 55 in an aligned mode, the ten notches 532 of the three cam plates 53 are arranged on the corresponding ten notches 532 of the four cam plates 55 in an aligned mode, then the two adjusting handles 52 are locked on the two threaded holes 531, and finally the lower mounting cover 51 is arranged on the middle cavity 32 by screws to fix the adjusting and locking part 5.

The above is the installation procedure of a single variable diameter core ball 2, and the procedure is repeated in this way, so that a plurality of variable diameter core balls 2 can be obtained, and then the installation procedure of the variable diameter core ball chain is explained. The second adjustment handle 52 in the adjustment locking part 5 for adjusting the variable diameter core ball 2 is used for placing the second ten retraction blocks 54 in an open state, the head of the other variable diameter core ball 2 is placed in the ball groove, then the second adjustment handle 52 is used for retracting the second ten locking blocks 54, and finally the lower mounting cover 51 and the cam disc 53 are fixed by using pins to prevent falling off during movement. And repeating the steps for multiple times, and adjusting the number of the core balls according to the requirement to obtain the variable-diameter core ball chain.

The mandrel is then installed as shown in figure 4. The second cam plate 15 is mounted on the first mounting groove 121 of the core rod main body 12 through screws, the second guide posts 142 of the first ten locking blocks 14 are mounted on the corresponding second ten notches 151 of the second cam plate 15 in an aligned mode, the first ten notches 132 of the first cam plate 13 are mounted on the corresponding first ten notches 132 of the second cam plate 15 in an aligned mode, the first adjusting handle 16 is locked on the first threaded hole 131, and finally the upper cover 11 of the core rod is mounted on the core rod main body 12 through screws. According to the steps, the installed variable diameter core ball chain can be installed on the mandrel, and the variable diameter mandrel is obtained.

The working process or working principle of the variable-diameter core rod for bending and forming the aerospace ultrathin-wall pipe is as follows.

When in use, the servo motor 42 is controlled to obtain the radius of the core ball which is required by the user, the first adjusting handle 16 is adjusted, the variable-diameter core ball 2 is installed on the core rod 1, and the lower installation cover 51 and the cam disc III 53 are connected together by the pin, so that the two variable-diameter core balls 2 can be prevented from falling off. Finally, adjusting the second adjusting handle 52 according to the number of the core balls required by the user, sequentially installing the variable-diameter core balls 2 to form a variable-diameter core ball chain, and finally obtaining the whole of the core rod and the variable-diameter core ball chain, wherein the whole can be placed in an aviation pipe to realize pipe bending.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and although the invention has been described in detail with reference to the foregoing examples, it will be apparent to those skilled in the art that various changes in the form and details of the embodiments may be made and equivalents may be substituted for elements thereof. All modifications, equivalents and the like which come within the spirit and principle of the invention are intended to be included within the scope of the invention.

Claims

1. A variable-diameter core rod for bending and forming an aerospace ultrathin-wall pipe is characterized by comprising a core rod (1) and a variable-diameter core ball chain; wherein the variable-diameter core ball chain is formed by matching a plurality of variable-diameter core balls (2) through a ball hinge;

the mandrel (1) comprises a mandrel upper top cover (11), a mandrel main body (12), a cam disc I (13), a locking block I (14), a cam disc II (15) and an adjusting handle I (16); the upper top cover (11) is fixedly connected to the core rod main body (12); a core rod locking mechanical mechanism assembled by the cam disc I (13), the locking block I (14) and the cam disc II (15) is positioned in the upper top cover (11); the second cam disc (15) is fixedly connected to the core rod main body (12); a plurality of first notches (132) and second notches (151) are respectively arranged on the first cam plate (13) and the second cam plate (15); the upper surface and the lower surface of the first locking block (14) are respectively provided with a first guide pillar (141) and a second guide pillar (142), and the opening and closing of the first locking block (14) are realized through the matching of the first guide pillar (141) and the first notch (132) and the matching of the second guide pillar (142) and the second notch (151); the adjusting handle I (16) is assembled on the cam disc I (13) and used for adjusting the opening and closing of the locking block I (14);

the variable diameter core ball (2) comprises a main body supporting part (3), a core ball diameter adjusting part (4) and an adjusting and locking part (5); the ball body of the variable-diameter core ball (2) is embedded into a core rod locking mechanical mechanism of the core rod (1), diameter changing is realized through the core ball diameter adjusting part (4), and spherical hinge matched locking of the variable-diameter core ball (2) is realized through the adjusting locking part (5).

2. The variable-diameter mandrel for bending and forming the aerospace ultra-thin wall pipe according to claim 1, wherein the main body supporting part (3) comprises an upper mounting cover (31), a middle cavity (32), an arc supporting block (33), a supporting rod (34), a middle section connecting slide block (35) and a motor mounting plate (36);

the upper mounting cover (31) is fixedly connected with the middle cavity (32); the arc supporting blocks (33) are uniformly arranged around the middle cavity (32); each arc supporting block (33) is fixedly connected with the middle section connecting slide block (35) through two supporting rods (34); the motor mounting plate (36) is mounted on the middle cavity (32).

3. The variable-diameter mandrel for bending and forming the aerospace ultra-thin wall pipe according to claim 2, wherein the mandrel diameter adjusting part (4) comprises a threaded transmission shaft (41), a motor (42), a small pin gear (43), a large pin gear (44), a coupler (45), a driving shaft (46), a ball bearing (47) and a bearing seat (48);

the number of the threaded transmission shafts (41) is equal to that of the middle connecting sliding blocks (35), and the threaded transmission shafts and the middle connecting sliding blocks are connected in a threaded fit mode; the shaft head of the threaded transmission shaft (41) is fixedly connected with a small pin gear (43); the motor (42) is arranged on the motor mounting plate (36) and is connected with a driving shaft (46) through a coupling (45), and the driving shaft (46) is fixedly connected with the large pin gear (44); the ball bearing (47) is connected with the bearing seat (48) through interference fit; the bearing block is fixedly connected to the middle cavity (32); the threaded transmission shaft (41) is supported on the intermediate cavity (32) through the ball bearing (47); the threaded transmission shaft (41) is in threaded connection with the middle section connecting slide block (35);

the motor (42) drives the driving shaft (46) to rotate, and then drives the large pin gear (44) to rotate; big round pin gear (44) transmit rotary motion for little round pin gear (43) through the gear cooperation, rotary motion is done through driving transmission shaft (41) to little round pin gear (43), transmission shaft (41) drive through the screw thread transmission middle section link block (35) slide, further drive circular arc supporting shoe (33) and do radial rectilinear motion, realize the reducing.

4. The variable-diameter mandrel for bending and forming the aerospace ultra-thin wall pipe according to claim 3, wherein the adjusting and locking part (5) comprises a lower mounting cover (51), a second adjusting handle (52), a third cam disc (53), a second locking block (54), a fourth cam disc (55) and a second supporting column (56);

the lower mounting cover (51) is fixedly connected to the middle cavity (32); a core ball locking mechanical mechanism consisting of the cam disc four (55), the locking block two (54) and the cam disc three (53) is positioned between the lower mounting cover (51) and the mounting groove two (322) of the middle cavity (32); a plurality of notches four (551) are formed in the cam disc four (55), a plurality of notches three (532) are formed in the cam disc three (53), guide pillars four (542) and guide pillars three (541) are respectively arranged on the upper surface and the lower surface of the locking block two (54), and the locking block two (54) is opened and closed through the matching of the guide pillars four (542) and the notches four (551) and the matching of the guide pillars three (541) and the notches three (532); the second adjusting handle (52) is assembled on the third cam disc (53) and used for adjusting the opening and closing of the second locking block (54).

5. The variable-diameter mandrel for bending and forming an aerospace ultra-thin wall pipe according to claim 4, wherein the number of the arc supporting blocks (33) is six; six middle section connecting slide blocks (35) are provided, and twelve supporting rods (34) are provided.