CN111136130A

CN111136130A - Shaft tube part straightening device and process method

Info

Publication number: CN111136130A
Application number: CN201911391150.9A
Authority: CN
Inventors: 赵军; 孟庆党; 于高潮; 穆振凯; 黄学颖; 王浩然
Original assignee: Yanshan University
Current assignee: Yanshan University
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2020-05-12
Anticipated expiration: 2039-12-30
Also published as: CN111136130B

Abstract

The invention discloses a straightening device and a process method for shaft tube parts, belonging to the technical field of machining and devices, wherein the straightening device comprises two sets of straightening mechanisms which are arranged on a workbench and are bilaterally symmetrical, a connecting rod mechanism used for transmitting motion and amplifying force, a hydraulic system used for providing power and a numerical control system used for controlling and commanding, the straightening mechanisms are arranged at the upper part of the workbench, the bottom end of a U-shaped plate in each straightening mechanism is hinged with the connecting rod mechanism, the connecting rod mechanism is also hinged with the lower end of a workbench plate, the connecting rod mechanism is connected with the hydraulic system, the hydraulic system and motors in the two sets of straightening mechanisms are connected with the numerical control system, and the process method comprises ① clamping, ② loading and ③ unloading.

Description

Shaft tube part straightening device and process method

Technical Field

The invention relates to the technical field of machining and devices, in particular to a shaft-tube part straightening device and a process method.

Background

The steel industry is one of the prop industries of national economy, and plays an irreplaceable role in the industrial modernization process of China. As an important steel product, shaft tube parts are widely applied to the industries of machinery, ships, petrochemical industry and the like, the precision requirement of people on the shaft tube parts is higher and higher along with the expansion of the production scale of the shaft tube parts, and the precision forming is more and more concerned by academia and steel enterprises.

Shaft parts often cause the straightness of a shaft to exceed standard due to the influence of heat treatment process, uneven material properties and processing process parameters; the pipe parts are affected by factors such as forming equipment and welding thermal stress, and the straightness of the pipe parts is often out of standard. The straightness of the shaft tube part exceeds the standard, so that the service life is greatly reduced, and even accidents can be caused under severe conditions. Therefore, in the production process of shaft tube parts, straightening is a necessary process, and straightening equipment is indispensable processing equipment.

At present, most of enterprises in China straighten shaft tube parts by adopting a pressure straightening method mainly because the pressure straightening method is simple and can straighten a large number of shaft tube parts with the same size; the straightening stroke is mostly determined by operators according to experience and estimation in the implementation of the pressure straightening process, and the traditional method has the defects of high labor intensity, low production efficiency and no guarantee on the stability of the straightening precision. When the shaft tube type part with larger initial deflection or multi-direction deflection is straightened, the shaft tube type part needs to be detected and pressed for many times, and the straightening efficiency is lower. In order to solve the defect of low pressure straightening efficiency, a two-roller continuous straightening process is developed. The shaft tube type parts rotate in the roll gaps to advance, go through the same loading path, unify the curvature to zero, and the shaft tube type parts are straightened. However, the two-roll straightening process cannot straighten parts such as stepped shafts and shaft tubes with diameters larger than a certain degree, and surface quality defects are easily generated. In a competitive environment with high quality and poor quality, the product quality becomes the key for the survival and development of enterprises, and in order to avoid the defects of the straightening method, the development of a novel accurate and efficient shaft pipe part straightening process method becomes the urgent need of the enterprises.

Disclosure of Invention

The invention aims to solve the technical problem of providing a shaft tube part straightening device and a process method, which are suitable for straightening shaft tube parts with over-standard straightness, can straighten pipe fittings and solid or hollow optical shafts or stepped shafts by designing the shaft tube part straightening device and applying the shaft tube part straightening device to a straightening process, have simple equipment, reduce straightening cost, improve straightening precision, ensure that the straightened shaft tube parts can obtain uniform residual stress, and improve the mechanical property of products.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a straightening device for shaft tube parts comprises two sets of straightening mechanisms which are arranged on a workbench and are bilaterally symmetrical, a connecting rod mechanism used for transmitting movement and amplifying force, a hydraulic system used for providing power and a numerical control system used for controlling and commanding; the straightening mechanism is arranged at the upper part of the workbench; the bottom end of a U-shaped plate in the straightening mechanism is hinged with a connecting rod mechanism, and the connecting rod mechanism is also hinged with the lower end of a workbench plate; the link mechanism is connected with the hydraulic system; the hydraulic system and the motors in the two straightening mechanisms are connected with the numerical control system.

The technical scheme of the invention is further improved as follows: the straightening mechanism comprises a chuck, two sets of bearing seat assemblies, a coupler, a pin shaft, two L-shaped plates with reinforcing ribs, a motor, a U-shaped plate with a dovetail-shaped guide rail at the bottom and a flat plate with a dovetail groove at the bottom; the two L-shaped plates are symmetrically and fixedly arranged on the workbench from front to back; a through hole is formed above the side plate of each L-shaped plate, and the U-shaped plate with the round through hole is hinged between the side plates of the two L-shaped plates through a pin shaft; the U-shaped plate with the dovetail-shaped guide rail at the bottom is provided with an upward opening, and the bottom surface of the U-shaped plate is not contacted with the workbench; the U-shaped plate is clamped with the flat plate provided with the dovetail groove through the guide rail; a plurality of threaded holes are arranged at intervals in the center of the plane where the side plate of the U-shaped plate is contacted with the two sides of the flat plate, and the U-shaped plate is fixedly connected with the flat plate through threaded connection; the motor is fixedly arranged on the flat plate through bolts; the motor is connected with the chuck through a coupler, and two bearing seat assemblies which are fixed on the flat plate and play a supporting role are connected between the coupler and the chuck.

The technical scheme of the invention is further improved as follows: the through hole formed above the side plate of the L-shaped plate is that the middle section is rectangular and the two ends are semicircular.

The technical scheme of the invention is further improved as follows: the flat plate can slide in the U-shaped plate.

The technical scheme of the invention is further improved as follows: two chucks respectively arranged on the two straightening mechanisms are parallel in initial position and vertically arranged on two end faces, and the two axes are superposed.

The technical scheme of the invention is further improved as follows: the connecting rod mechanisms are bilaterally symmetrical and comprise a first connecting rod, a second connecting rod and a third connecting rod, wherein the upper end of the first connecting rod is hinged with the bottom end of the U-shaped plate, the second connecting rod is initially parallel to the workbench and is hinged with the lower end of the workbench bedplate, and one end of the third connecting rod is hinged with a hydraulic cylinder in the hydraulic system; the first connecting rod vertically penetrates through a rectangular through hole formed in the workbench, and the lower end of the first connecting rod is hinged with the second connecting rod; the other end of the second connecting rod is hinged with the third connecting rod.

The invention also provides a process method for straightening the shaft-tube parts, which comprises the following steps:

the method comprises the following steps: clamping; the initial positions of the two chucks are parallel, two end faces of the two chucks are vertically placed, the two axes are overlapped, the clamping diameters of the two chucks are adjusted to enable the clamping diameters of the two chucks to be larger than the diameter of the shaft tube part to be straightened, and two ends of the shaft tube part to be straightened are respectively placed between the two chucks and clamped; when the two chucks clamp, the corrected shaft tube part with initial deflection is straightened, namely the axis is approximately a straight line; when in alignment, the straight line distance at two ends of the shaft-corrected tube part is extended, so that the chucks at two ends have certain horizontal displacement;

step two: loading; the reference points which can carry out horizontal displacement are respectively supposed to be arranged at the positions with the same distance at the outer sides of the axes of the two chucks, the reference points correspond to the middle points of connecting lines of connecting points of a U-shaped plate and L-shaped plates at the front side and the rear side in the device, the reference point at one side and the chucks can be regarded as rigid connection, the chucks at the two ends are started simultaneously and rotate around the axes of the chucks at the same speed and the same direction, the left chuck rotates anticlockwise around the left reference point while rotating, the right chuck rotates clockwise around the right reference point, and parts such as corrected shaft pipes are bent towards the upper side in a; at the moment, the horizontal distance between the two reference points is gradually shortened in a small way, along with the gradual increase of the bending degree of the shaft-corrected pipe part, the proportion of plastic deformation to the whole deformation is larger, and the shaft-corrected pipe part rotates around the axis of the shaft-corrected pipe part while the bending degree is increased, namely any longitudinal fiber of the shaft-corrected pipe part undergoes alternate positive and negative bending for many times;

step three: unloading; after the straightened shaft tube type part is bent to a certain degree, the chucks at the two ends begin to unload, namely, the chucks at the two ends rotate around the axes of the chucks at the same angular speed as that in the loading process, the left chuck rotates clockwise around a left reference point, and the right chuck rotates anticlockwise around a right reference point; until the two chucks return to the parallel state, namely the parts such as the shaft correcting tube reach the straight state; and (3) gradually increasing the horizontal distance between the two reference points in the unloading process to a small extent, finally loosening the two chucks, taking out the parts such as the corrected shaft tube, and finishing the straightening.

The technical scheme of the invention is further improved as follows: when the initial deflection of the straightened shaft tube part is large, a round roller needs to be arranged on the front side or the rear side of the shaft tube part.

Due to the adoption of the technical scheme, the invention has the technical progress that:

1. the shaft tube part straightening device is provided with two sets of straightening mechanisms which are bilaterally symmetrical and the connecting rod mechanisms, so that the shaft tube part which is bent in multiple directions can be straightened at one time, the problem that the conventional pressure straightening process can only straighten the deflection in one direction at a time, when the deflection in multiple directions exists, the deflection in each direction needs to be straightened respectively, the efficiency is low, and plastic hinge is easy to cause straightening failure is solved.

2. The shaft tube part straightening device provided by the invention overcomes the limitation that the existing reciprocating bending and straightening process can only straighten an optical axis or a tube by ingeniously arranging the structural connection of the U-shaped plate, the L-shaped plate and the plate structure in the straightening mechanism, can straighten a pipe fitting and a solid or hollow optical axis or stepped shaft, successfully enlarges the straightening range and has high straightening success rate.

3. The shaft tube part straightening device provided by the invention has the advantages that through the equipment with the two parallel chucks, the straightened shaft tube part is not collided or rubbed by an external object in the straightening process, and the shaft tube part with over-standard deflection and the like are straightened by the device, so that the surface of the shaft tube part is free from defects such as abrasion, scratch and the like.

4. The straightening device for the shaft tube type parts is designed and applied to the straightening process, the device is simple, the operation is convenient, the straightening cost is reduced, the straightening precision is improved, the straightened shaft tube type parts can obtain uniform residual stress, and the mechanical property of the product is improved.

Drawings

FIG. 1 is a front view of a straightening apparatus according to the present invention;

FIG. 2 is an isometric view of a straightener of the present invention;

FIG. 3 is a schematic view of the U-shaped plate and plate structure of the present invention;

FIG. 4 is a schematic diagram of example 1 of the present invention before straightening;

FIG. 5 is a schematic diagram of embodiment 1 of the invention after clamping is completed;

FIG. 6 is a schematic diagram of the loading process in example 1 of the present invention;

FIG. 7 is a schematic view during the unloading in the embodiment 1 of the present invention;

FIG. 8 is a schematic diagram of the embodiment 1 of the present invention after straightening;

FIG. 9 is an elevation view of the straightening process of example 3 of the present invention;

FIG. 10 is a top view of the straightening process in example 3 of the present invention.

The device comprises a shaft to be straightened tube part 1, a chuck 2, a bearing seat assembly 3, a shaft coupler 4, a pin shaft 5, a pin shaft 6, an L-shaped plate 7, a motor 8, a U-shaped plate 9, a workbench 10, a hydraulic cylinder 11, a first connecting rod 12, a second connecting rod 13, a third connecting rod 14, a flat plate 15 and a round roller.

Detailed Description

The present invention is further illustrated in detail below with reference to examples:

as shown in figures 1-3, a shaft tube part straightening device is characterized in that: comprises two sets of straightening mechanisms which are arranged on a workbench 9 and are bilaterally symmetrical, a connecting rod mechanism used for transmitting movement and amplifying force, a hydraulic system used for providing power and a numerical control system used for controlling and commanding; the straightening mechanism is arranged at the upper part of the workbench 9; the bottom end of a U-shaped plate 8 in the straightening mechanism is hinged with a connecting rod mechanism, and the connecting rod mechanism is also hinged with the lower end of a table plate 9 of a workbench; the link mechanism is connected with the hydraulic system; the hydraulic system and the motors 7 in the two straightening mechanisms are connected with a numerical control system.

The straightening mechanism comprises a chuck 2, two sets of bearing seat assemblies 3, a coupler 4, a pin shaft 5, two L-shaped plates 6 with reinforcing ribs, a motor 7, a U-shaped plate 8 with a dovetail-shaped guide rail at the bottom and a flat plate 14 with a dovetail groove at the bottom; the two L-shaped plates are symmetrically and fixedly arranged on the workbench 9 from front to back; a through hole with a rectangular middle section and semicircular two ends is formed above the side plate of each L-shaped plate 6, and the through hole is arranged to ensure that the straightening mechanism has certain horizontal displacement during straightening; the U-shaped plate 8 with the circular through hole is hinged between the side plates of the two L-shaped plates 6 through a pin shaft 5; the U-shaped plate 8 with the dovetail-shaped guide rail arranged at the bottom has an upward opening, and the bottom surface of the U-shaped plate is not contacted with the workbench 9; the U-shaped plate 8 and the flat plate 14 with the dovetail groove are clamped with the dovetail groove through the guide rail, and the flat plate 14 can slide in the U-shaped plate 8; the center position of a plane where the side plate of the U-shaped plate 8 is in contact with the two sides of the flat plate 14 is provided with a plurality of threaded holes at intervals, the U-shaped plate 8 is fixedly connected with the flat plate 14 through threaded connection, and the U-shaped plate 8 is connected with the flat plate 14 through the threads so as to adjust the horizontal distance between the two chucks 2 when the shaft tube type part 1 to be straightened is placed, and ensure that the shaft tube type parts 1 with different lengths can be straightened; the motor 7 is fixedly arranged on the flat plate 14 through bolts; the motor 7 is connected with the chuck 2 through a coupling 4, and two bearing seat assemblies 3 which are fixed on a flat plate 14 for supporting are connected between the coupling 4 and the chuck 2. Two chucks 2 respectively arranged on two straightening mechanisms are parallel in initial position and vertically arranged on two end faces, and the two axes are superposed.

As shown in fig. 1, the link mechanism is bilaterally symmetrical and comprises a first link 11 with the upper end hinged to the bottom end of the U-shaped plate 8, a second link 12 initially parallel to the workbench 9 and hinged to the lower end of the bedplate of the workbench 9, and a third link 13 with one end hinged to a hydraulic cylinder 10 in a hydraulic system; the first connecting rod 11 vertically penetrates through a rectangular through hole formed in the workbench 9, and the lower end of the first connecting rod is hinged with the second connecting rod 12; the other end of the second connecting rod 12 is hinged with the third connecting rod 13. And the connecting rods 13 at the two ends are hinged with a hydraulic system. The function of the linkage is to transfer motion and amplify the force provided by the hydraulic system. The link mechanism can provide that the left side chuck rotates anticlockwise around a left reference point and the right side chuck rotates clockwise around a right reference point when the chucks rotate around the axes of the chucks, so that the force generated when the straightened shaft tube part 1 is bent upwards in a protruding mode is the same as that generated when the straightened shaft tube part is bent reversely.

the method comprises the following steps: clamping; the two chucks 2 are parallel in initial position, two end faces are vertically arranged, the two axes are overlapped, the clamping diameters of the two chucks 2 are adjusted, the clamping diameters of the two chucks 2 are larger than the diameter of the corrected shaft tube part 1, and two ends of the corrected shaft tube part 1 are respectively placed between the two chucks 2 and clamped; while the two chucks 2 clamp, the corrected shaft 1 with certain initial deflection is straightened, namely the axis is approximately a straight line; when in alignment, the straight line distance at two ends of the shaft-corrected tube part 1 slightly extends, and the chucks 2 at two ends horizontally displace to two sides;

step two: loading; the reference points which can carry out certain horizontal displacement are respectively supposed to be arranged at the same distance positions outside the axes of the two chucks 2, the reference points correspond to the middle points of connecting lines of connecting points of the U-shaped plates 8 and the L-shaped plates 6 at the front side and the rear side in the device, the reference point at one side and the chucks 2 can be regarded as rigid connection, the chucks 2 at the two ends are started simultaneously and rotate around the axes of the chucks at the same speed in the same direction, the left chuck rotates anticlockwise around the left reference point during rotation, the right chuck rotates clockwise around the right reference point, and the straightened shaft tube part 1 is bent towards the upper side in a protruding mode; at the moment, the horizontal distance between the two reference points is gradually shortened in a small way, along with the gradual increase of the bending degree of the shaft-corrected tube part 1, the proportion of plastic deformation to the whole deformation is larger, and the shaft-corrected tube part 1 rotates around the axis of the shaft-corrected tube part 1 while the bending degree is increased, namely any longitudinal fiber of the shaft-corrected tube part 1 undergoes alternate positive and negative bending for many times;

step three: unloading; after the straightened shaft tube type part 1 is bent to a certain degree, the chucks 2 at the two ends start to unload, namely, the left chuck rotates clockwise around a left reference point and the right chuck rotates anticlockwise around a right reference point while the chucks 2 at the two ends rotate around the axis of the chucks at the same angular speed as that in the loading process; until the two chucks return to the parallel state, namely the shaft correcting pipe type part 1 reaches the straight state; and (3) gradually increasing the horizontal distance between the two reference points in the unloading process to a small extent, finally loosening the two chucks, taking out the part 1 such as the corrected shaft tube, and finishing the straightening.

When the initial deflection of the shaft-corrected pipe type part 1 is large, a round roller 15 needs to be arranged on the front side or the rear side of the shaft-corrected pipe type part 1. If the initial deflection of the shaft tube part 1 to be straightened is larger than a certain degree, the shaft tube part 1 to be straightened swings at the front side and the rear side in the straightening process, so that the straightening effect is poor; at the moment, a round roller 15 with certain diameter and length can be placed on the front side or the rear side of the shaft straightening pipe part 1, and the round roller 15 can rotate around the axis of the round roller 15.

The electric motor 7 connected with the chuck 2 in the device can be replaced by a hydraulic motor; the hydraulic system for providing power for bending the shaft straightening pipe part 1 can be replaced by an electric system, and the hydraulic system can be flexibly selected according to actual requirements.

The specific use method comprises the following steps:

take a solid optical axis with a diameter of 30mm and a length of 500mm as an example of the shaft-corrected tube part 1. The mechanical properties of the solid optical axis are as follows: the elastic model is 210GPa, the yield limit is 345MPa, the plastic modulus is 2160MPa, and the Poisson ratio is 0.3. The fitting initial deflection of the shaft straightening pipe part 1 is 0.8 mm.

As shown in FIG. 4, the two chucks 2 are vertically and parallelly arranged on the end surfaces, and the two axes are superposed; the reference points which can carry out certain horizontal displacement are respectively arranged at the same distance positions on the outer sides of the axes of the two chucks 2;

as shown in fig. 5, the clamping diameter of the chuck 2 is adjusted to be larger than the diameter of the shaft tube part to be straightened, and the two ends of the shaft tube part 1 to be straightened are respectively placed into the two chucks and clamped;

as shown in fig. 6, then the chucks at both ends start to rotate around the respective axes to the outside at an angular velocity of 10 rad/s; meanwhile, the left chuck rotates anticlockwise around the left reference point in the vertical plane at the angular speed of 0.14rad/s, and the right chuck rotates clockwise around the right reference point in the vertical plane at the angular speed of 0.14 rad/s;

as shown in fig. 7, during the loading process, the bending deformation of the shaft-corrected pipe-like component 1 is larger and larger while rotating around its axis, any longitudinal fiber on the shaft undergoes multiple reciprocating bending, and once the shaft rotates for one circle, any longitudinal fiber on the shaft completes one reciprocating bending (i.e. positive and negative bending). The loading process lasts for 10s, and the unloading process is started after 10s, namely the left chuck rotates clockwise around a left reference point in a vertical plane at an angular speed of 0.14rad/s, the right chuck rotates anticlockwise around a right reference point in the vertical plane at an angular speed of 0.14rad/s, and meanwhile, the chucks keep moving around the self axis in the same size and direction as the movement in the loading process;

as shown in fig. 8, when the chucks at the two ends return to the initial state, the pipe-to-be-straightened component 1 also reaches a straight state, and the pipe-to-be-straightened component 1 is taken out, so that the straightening work is completed. Straightening a pipe, a hollow shaft and a stepped shaft, and steps

Similarly, only the degree of bending needs to be changed to prevent excessive plastic deformation, resulting in straightening failure.

As shown in fig. 9 and 10, if the initial deflection of the straightened shaft pipe part is greater than a certain degree, the straightened shaft pipe part 1 swings back and forth in the straightening process, so that the straightening effect is poor; in this case, a circular roller 15 with a certain diameter and length can be placed on the front side or the rear side of the shaft tube type part 1, and the circular roller 15 can rotate around the axis. The round roller 15 is horizontally arranged, the centroid of the round roller 15 is located in the middle of the two chucks in the horizontal direction, the centroid of the round roller 15 is located in a certain position between the highest point and the lowest point of the shaft pipe part in the straightening process in the vertical direction, the distance between the outer edge of the straightened shaft pipe part and the front and back of the outer edge of the round roller is zero, and after the round roller 15 is added, the front and back swing of the shaft pipe part in the straightening process can be limited, and a better straightening effect is achieved.

In conclusion, the straightening device for the shaft tube parts is designed and applied to the straightening process, is suitable for straightening the shaft tube parts with over-standard deflection, can be used for straightening a straight tube and a solid or hollow optical shaft or stepped shaft, is simple in equipment and convenient to operate, reduces the straightening cost, improves the straightening precision, enlarges the straightening range, can obtain uniform residual stress for the straightened shaft tube parts, and improves the mechanical property of the product.

Claims

1. The utility model provides a shaft tube part straightener which characterized in that: comprises two sets of straightening mechanisms which are arranged on a workbench (9) and are bilaterally symmetrical, a connecting rod mechanism used for transmitting movement and amplifying force, a hydraulic system used for providing power and a numerical control system used for controlling and commanding; the straightening mechanism is arranged at the upper part of the workbench (9); the bottom end of a U-shaped plate (8) in the straightening mechanism is hinged with a connecting rod mechanism, and the connecting rod mechanism is also hinged with the lower end of a table plate of a workbench (9); the link mechanism is connected with the hydraulic system; the hydraulic system and the motors (7) in the two straightening mechanisms are connected with the numerical control system.

2. The straightening device for the shaft-tube parts as claimed in claim 1, wherein the straightening device comprises: the straightening mechanism comprises a chuck (2), two sets of bearing seat assemblies (3), a coupler (4), a pin shaft (5), two L-shaped plates (6) with reinforcing ribs, a motor (7), a U-shaped plate (8) with a dovetail-shaped guide rail at the bottom and a flat plate (14) with a dovetail groove at the bottom; the two L-shaped plates are symmetrically and fixedly arranged on the workbench (9) from front to back; a through hole is formed above the side plate of each L-shaped plate (6), and a U-shaped plate (8) with a round through hole is hinged between the side plates of the two L-shaped plates (6) through a pin shaft (5); the U-shaped plate (8) with the dovetail-shaped guide rail arranged at the bottom is opened upwards, and the bottom surface of the U-shaped plate is not contacted with the workbench (9); the U-shaped plate (8) is clamped with the flat plate (14) with the dovetail groove through the guide rail; a plurality of threaded holes are arranged at intervals in the center of a plane where the side plate of the U-shaped plate (8) is in contact with the two sides of the flat plate (14), and the U-shaped plate (8) is fixedly connected with the flat plate (14) through threaded connection; the motor (7) is fixedly arranged on the flat plate (14) through bolts; the motor (7) is connected with the chuck (2) through the shaft coupling (4), and two sets of bearing seat assemblies (3) which are fixed on the flat plate (14) and play a supporting role are connected between the shaft coupling (4) and the chuck (2).

3. The straightening device for the shaft-tube parts as claimed in claim 2, wherein: the through hole formed above the side plate of the L-shaped plate (6) is a rectangle with two semicircular ends at the middle section.

4. The straightening device for the shaft-tube parts as claimed in claim 2, wherein: the flat plate (14) can slide in the U-shaped plate (8).

5. The straightening device for the shaft-tube parts as claimed in claim 2, wherein: two chucks (2) respectively arranged on the two straightening mechanisms are parallel in initial position and vertically arranged on two end faces, and the two axes are superposed.

6. The straightening device for the shaft-tube parts as claimed in claim 1, wherein the straightening device comprises: the connecting rod mechanisms are bilaterally symmetrical and comprise a first connecting rod (11) with the upper end hinged to the bottom end of the U-shaped plate (8), a second connecting rod (12) which is parallel to the workbench (9) in an initial state and hinged to the lower end of a bedplate of the workbench (9), and a third connecting rod (13) with one end hinged to a hydraulic cylinder (10) in a hydraulic system; the first connecting rod (11) vertically penetrates through a rectangular through hole formed in the workbench (9), and the lower end of the first connecting rod is hinged with the second connecting rod (12); the other end of the second connecting rod (12) is hinged with the third connecting rod (13).

7. A shaft tube part straightening process method is characterized by comprising the following steps: the method comprises the following steps:

the method comprises the following steps: clamping; the initial positions of the two chucks (2) are parallel, two end faces of the two chucks are vertically arranged, the two axes are overlapped, the clamping diameters of the two chucks (2) are adjusted, the clamping diameters of the two chucks (2) are larger than the diameter of the shaft-corrected tube part (1), and two ends of the shaft-corrected tube part (1) are respectively placed between the two chucks (2) and clamped; when the two chucks (2) are clamped, the corrected shaft tube part (1) with initial deflection is straightened, namely the axis is approximately a straight line; when in alignment, the straight line distance at two ends of the shaft-corrected tube part (1) is extended, and the chucks (2) at two ends horizontally displace towards two sides;

step two: loading; the reference points which can carry out horizontal displacement are respectively supposed to be arranged at the same distance positions outside the axes of the two chucks (2), the reference points correspond to the middle points of connecting lines of connecting points of a U-shaped plate (8) and L-shaped plates (6) on the front side and the rear side in the device, the reference point on one side and the chucks (2) can be regarded as rigid connection, the chucks (2) on the two ends are started simultaneously and rotate around the axes of the chucks at the same speed in the same direction, the left chuck rotates anticlockwise around the left reference point while rotating, and the right chuck rotates clockwise around the right reference point, so that parts (1) of the corrected shaft tube are bent upwards in a protruding mode; at the moment, the horizontal distance between the two reference points is gradually shortened in a small way, along with the gradual increase of the bending degree of the shaft-corrected tube part (1), the proportion of plastic deformation to the whole deformation is larger, the bending degree is increased, and meanwhile, the shaft-corrected tube part (1) always rotates around the axis of the shaft-corrected tube part (1), namely, any longitudinal fiber of the shaft-corrected tube part (1) undergoes alternate positive and negative bending for many times;

step three: unloading; after the straightened shaft tube part (1) is bent to a certain degree, the chucks (2) at the two ends start to unload, namely, the chucks (2) at the two ends rotate around the axis of the chucks at the same angular speed as that in the loading process, the left chuck rotates clockwise around a left reference point, and the right chuck rotates anticlockwise around a right reference point until the two chucks return to a parallel state, namely, the straightened shaft tube part (1) reaches a straight state; and (3) gradually increasing the horizontal distance between the two reference points in the unloading process to a small extent, finally loosening the two chucks (2), taking out the parts (1) such as the corrected shaft tube, and finishing the straightening.

8. The straightening process method for the shaft-tube parts as claimed in claim 7, wherein the straightening process method comprises the following steps: when the initial deflection of the shaft-corrected pipe part (1) is large, a round roller (15) needs to be arranged on the front side or the rear side of the shaft-corrected pipe part (1).