A barrel straightness measuring device

Abstract

The utility model provides a kind of barrel straightness measuring device, including laser transmitter, measuring structure and limit guide structure;Measuring structure includes centering mechanism, photoelectric position sensitive detector, push rod, magnetic scale and read magnetic head, push rod is installed on limit guide structure, push rod can only reciprocate along its axial direction;Magnetic scale is fixed on the side wall of push rod, read magnetic head is fixed on limit guide structure, for inductive grid distance on magnetic scale;Photoelectric position sensitive detector is located at the end of centering mechanism towards laser transmitter, centering mechanism is connected to the end of push rod towards laser transmitter by elastic coupling, to make push rod push centering mechanism reciprocate in barrel, centering mechanism can be kept coaxial arrangement with barrel, centering mechanism cooperates with barrel inner wall, and under the action of external force, it can shrink and expand along its radial direction.The utility model has the advantages of high degree of automation, small barrel straightness measurement error.

Description

Technical Field

[0001] This utility model relates to the field of detection technology, specifically to a device for measuring the straightness of a tube. Background Technology

[0002] After undergoing complex manufacturing processes such as forging, machining, and heat treatment, the inner wall of an artillery barrel inevitably experiences millimeter-level radial deformation and bending due to residual stress, tool wear, and heat treatment deformation. This inherent geometric deviation directly causes the initial direction of the projectile to deviate from the theoretical trajectory upon leaving the barrel, severely reducing firing accuracy and potentially leading to a barrel explosion risk due to abnormal scraping between the projectile and the rifling. Therefore, precise straightness testing of the finished gun barrel is a crucial step in quantifying the deviation between its actual and ideal axes. This quality control step is indispensable for ensuring the accuracy and safety of artillery shells.

[0003] Currently, the main methods for testing the straightness of pipe tubes include the lever method, gauge inspection method, laser collimation method, image processing method, and PSD measurement method. Among these, the lever method and gauge measurement method are traditional methods with low accuracy and relatively low inspection efficiency. The laser collimation method, image processing method, and PSD measurement method, on the other hand, offer high accuracy and are considered more advanced methods. However, the laser collimation method has poor adaptability to different pipe diameters, making it difficult to achieve comprehensive and accurate measurements. The image processing method suffers from excessive computation and poor anti-interference capabilities.

[0004] The PSD (Position Sensitive Device) measurement method boasts high sensitivity and speed, with relatively low requirements for the size of the measured object, making it suitable for measuring tubes of varying diameters and lengths. A PSD is typically mounted on a centering mechanism, which, via a push rod, moves the centering mechanism and the PSD back and forth within the tube. A laser emitter is positioned on the outer side of the long tube axis, emitting a laser beam that illuminates the two-dimensional PSD. The PSD measures the position coordinates of the laser spot on a two-dimensional plane. The host computer processes this position information at different axial positions and fits a near-perfect virtual straight line using the least squares method. The deviation of this virtual straight line from the line connecting the centers of the two end faces of the long tube reflects the straightness deviation of the tube.

[0005] Due to optical interference, it is impossible to automatically measure the axial movement of the PSD using grating rulers or rangefinders. Manual recording is time-consuming and labor-intensive, hindering the promotion of automation. In addition, the large length-to-diameter ratio of the gun barrel means that, on the one hand, when the barrel straightness is poor, the centering mechanism is prone to getting stuck in the barrel, causing measurement obstruction; on the other hand, the centering mechanism is prone to offset inside the barrel, leading to increased measurement error of the spot coordinates. Utility Model Content

[0006] To address the problems in the background art, this utility model proposes a tube straightness measuring device with a high degree of automation and small measurement error.

[0007] The present invention adopts the following technical solution: A device for measuring the straightness of a tube includes a laser emitter, a measuring structure, and a limiting guide structure. The laser emitter and the limiting guide structure are respectively disposed on both sides of the tube in the axial direction. The laser emitter is used to send a laser beam parallel to the tube axis toward the inside of the tube. The measuring structure includes a centering mechanism, a photoelectric position-sensitive detector, a push rod, a magnetic scale, and a reading head. The push rod is mounted on the limiting guide structure, which is used to guide and limit the push rod so that the push rod can only move back and forth along its axial direction; the magnetic scale is fixed on the side wall of the push rod and arranged along the axial direction of the push rod; the reading head is fixed on the limiting guide structure and is used to sense the grid pitch on the magnetic scale. A photoelectric position-sensitive detector is located at the end of the centering mechanism facing the laser emitter to detect the position of the laser beam spot on it. The centering mechanism is connected to the end of the push rod facing the laser emitter via a flexible coupling, so that the centering mechanism can remain coaxial with the body tube during the reciprocating movement of the push rod in the tube. The centering mechanism cooperates with the inner wall of the body tube and can expand and contract in the radial direction under the action of external force to adapt to the radial changes of the body tube.

[0008] As a further improvement to the above technical solution: The limiting and guiding structure includes a base and a guide limiting seat mounted on the base. The guide limiting seat has a guide through hole that cooperates with the push rod. The guide through hole has a limiting through groove that cooperates with the magnetic scale. The push rod passes through the guide through hole and the magnetic scale passes through the limiting through groove. The reading head is mounted on the end of the guide limiting seat facing the magnetic scale via a bracket.

[0009] The limiting and guiding structure also includes a roller guide seat, which is located in front of the guide limiting seat along the direction of push rod movement, and the push rod passes through the roller guide seat.

[0010] The guide limit seat is mounted on the base via a mounting part. The guide limit seat and the mounting part are hinged together via a horizontal hinge shaft, which is arranged horizontally and perpendicular to the push rod axis.

[0011] The base has a sliding part on the side facing the mounting part, the mounting part is slidably connected to the sliding part, and a fastener is provided between the sliding part and the mounting part to fix the mounting part and the sliding part together.

[0012] The limiting and guiding structure also includes a mounting base, which is fixed on the base and has a mounting hole that mates with the body tube. One end of the body tube facing the mounting base passes through the mounting hole.

[0013] The flexible coupling includes a first connecting member, a second connecting member, a transition member, a first hinge shaft, and a second hinge shaft. The first connecting member is fixedly connected to the centering structure, and the second connecting member is fixedly connected to the push rod. The first connecting member and the transition member are hinged together through the first hinge shaft, and the second connecting member and the transition member are hinged together through the second hinge shaft. The first hinge shaft and the second hinge shaft are arranged axially perpendicularly.

[0014] The laser emitter is mounted on a support base with a shaft hole. The end of the laser tube facing the laser emitter passes through the shaft hole. The end of the support base facing the laser emitter has an aperture hole, and the central axis of the aperture hole coincides with the central axis of the shaft hole.

[0015] The centering structure includes a telescopic bushing, a fixed bushing, a movable bushing, and a spring. A photoelectric position-sensitive detector is installed at one end of the fixed bushing, and the other end of the fixed bushing is connected to a push rod. The telescopic bushing, the movable bushing, and the spring are sequentially fitted onto the fixed bushing. The outer wall of the telescopic bushing matches the inner wall of the tube, and the telescopic bushing can extend and retract radially under external force. The spring is compressed between the push rod and the movable bushing. One axial end of the inner wall of the telescopic bushing abuts against the fixed bushing through a first wedge structure, and the other axial end of the inner wall of the telescopic bushing abuts against the movable bushing through a second wedge structure. The first and second wedge structures are symmetrically arranged.

[0016] The telescopic bushing has multiple first radial through grooves and multiple second radial through grooves. The multiple first radial through grooves and multiple second radial through grooves are arranged alternately along the circumference of the telescopic bushing. The first radial through grooves extend axially along the telescopic bushing to the front end face that penetrates the telescopic bushing, and the second radial through grooves extend axially along the telescopic bushing to the rear end face that penetrates the telescopic bushing.

[0017] Compared with the prior art, the advantages of this utility model are: The tube straightness measuring device of this utility model uses a push / pull centering mechanism to reciprocate along the axial direction of the tube. The limiting guide structure ensures that the push rod does not rotate circumferentially and always maintains axial movement. The elastic coupling ensures that the centering mechanism does not become eccentric during the movement of the push / pull centering mechanism, and the centering mechanism itself can adapt to the radial changes of the tube. This ensures that the centering mechanism always remains coaxial and in close contact with the tube during its reciprocating movement along the axial direction of the tube. As a result, the coordinate center point of the photoelectric position sensitive detector (PSD) always coincides with the center of the inner hole cross section at various positions of the tube, thereby obtaining the precise position of the laser spot.

[0018] Furthermore, by mounting the magnetic scale on the side wall of the push rod and moving it axially with the push rod, and fixing the reading head on the limiting guide structure, the reading head obtains the axial position change of the PSD by sensing the change in the grating pitch on the magnetic scale. This enables the automated measurement of the axial displacement of the PSD and the position of the light spot at each axial displacement, and the magnetic scale structure does not interfere with the measurement of the light spot position. Attached Figure Description

[0019] To facilitate understanding of this invention, it will be described in more detail with reference to the specific embodiments shown in the accompanying drawings. These drawings depict only typical embodiments of this invention and should not be considered as limiting the scope of protection of this invention.

[0020] Figure 1 This is a three-dimensional structural schematic diagram of the tube straightness measuring device according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the application structure of the tube straightness measuring device according to an embodiment of the present invention.

[0022] Figure 3 This is an exploded structural diagram of the limiting and guiding structure in an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the application structure of the limiting and guiding structure in an embodiment of the present invention.

[0024] Figure 5 This is a cross-sectional structural diagram of the guide limiting seat in an embodiment of the present invention.

[0025] Figure 6 This is an exploded structural diagram of the flexible coupling in an embodiment of the present invention.

[0026] Figure 7 This is a cross-sectional structural diagram of the centering mechanism in an embodiment of the present invention.

[0027] Figure 8 This is a three-dimensional structural diagram of the telescopic bushing in an embodiment of the present invention.

[0028] Figure 9 This is a schematic diagram of the installation structure of the laser emitter in an embodiment of the present invention.

[0029] Figure label: 1. Laser emitter; 2. Measuring structure; 21. Photoelectric position sensitive detector; 22. Push rod; 23. Magnetic scale; 24. Reading head; 25. Telescopic bushing; 251. First radial through groove; 252. Second radial through groove; 26. Fixed bushing; 27. Movable bushing; 28. Spring; 29. ​​Protective cover; 3. Limiting guide structure; 31. Base; 32. Guide limiting seat; 321. Guide through hole; 322. Limiting through groove; 33. Roller guide seat; 34. Mounting part; 35. Horizontal hinge shaft; 36. Slide seat; 37. Fastener; 38. Mounting seat; 381. Mounting hole; 4. Flexible coupling; 41. First connecting piece; 42. Second connecting piece; 43. Adapter; 44. First hinge shaft; 45. Second hinge shaft; 5. Support seat; 51. Shaft hole; 52. Aperture hole; 53. Adjustment mechanism. Detailed Implementation

[0030] The embodiments of the present invention are described below with reference to the accompanying drawings, so that those skilled in the art can better understand and implement the present invention. However, the listed embodiments are not intended to limit the present invention. In the absence of conflict, the following embodiments and the technical features in the embodiments can be combined with each other, wherein the same components are indicated by the same reference numerals.

[0031] like Figure 1-9 As shown, this utility model provides a device for measuring the straightness of a tube, including a laser emitter 1, a measuring structure 2, and a limiting and guiding structure 3. The laser emitter 1 and the limiting guide structure 3 are respectively located on both sides of the tube in the axial direction. The laser emitter 1 is used to send a laser beam parallel to the tube axis toward the inside of the tube. The measuring structure 2 includes a centering mechanism, a photoelectric position sensitive detector 21, a push rod 22, a magnetic scale 23, and a reading head 24. The push rod 22 is mounted on the limiting guide structure 3, which is used to guide and limit the push rod 22 so that the push rod 22 can only move back and forth along its axial direction; the magnetic scale 23 is fixed on the side wall of the push rod 22 and arranged along the axial direction of the push rod 22; the reading head 24 is fixed on the limiting guide structure 3 and is used to sense the grid pitch on the magnetic scale 23. The photoelectric position sensitive detector 21 is located at the end of the centering mechanism facing the laser emitter 1 and is used to detect the position of the spot of the laser beam irradiating it. The centering mechanism is connected to the end of the push rod 22 facing the laser emitter 1 through the elastic coupling 4, so that the centering mechanism can be coaxially arranged with the body tube during the process of the push rod 22 pushing the centering mechanism to reciprocate in the body tube. The centering mechanism cooperates with the inner wall of the body tube and can expand and contract in the radial direction under the action of external force to adapt to the radial change of the body tube.

[0032] The push rod 22 pushes / pulls the centering mechanism to move back and forth along the axial direction of the tube 6. The limiting guide structure 3 ensures that the push rod 22 does not rotate circumferentially and always maintains axial movement. The elastic coupling 4 ensures that the centering mechanism does not become eccentric during the push / pull movement of the push rod 22. Furthermore, the centering mechanism itself can adapt to the radial changes of the tube 6. This ensures that the centering mechanism always remains coaxially arranged and in contact with the tube 6 during the reciprocating movement along the axial direction of the tube 6. As a result, the coordinate center point of the photoelectric position sensitive detector 21 (PSD) always coincides with the center of the inner hole cross section at each position of the tube 6, thereby obtaining a precise laser spot position.

[0033] Furthermore, by mounting the magnetic scale 23 on the side wall of the push rod 22 and moving it axially with the push rod 22, the reading head 24 is fixed on the limiting guide structure 3. The reading head 24 obtains the axial position change of the PSD by sensing the change in the grating pitch on the magnetic scale 23. This enables the automated measurement of the axial displacement of the PSD and the position of the light spot at each axial displacement, and the magnetic scale structure does not interfere with the measurement of the light spot position.

[0034] In this embodiment, the limiting guide structure 3 includes a base 31 and a guide limiting seat 32 mounted on the base 31. The guide limiting seat 32 has a guide through hole 321 that cooperates with the push rod 22. The guide through hole 321 has a limiting through groove 322 that cooperates with the magnetic grating ruler 23. The push rod 22 passes through the guide through hole, and the magnetic grating ruler 23 passes through the limiting through groove 322. The reading head 24 is mounted on the end of the guide limiting seat 32 facing the magnetic grating ruler 23 by a bracket.

[0035] The magnetic scale 23 is installed on the side wall of the push rod 22, and a limiting through groove 322 that cooperates with the magnetic scale 23 is opened on the wall of the guide through hole 321 on the guide limiting seat 32. This can achieve both axial guidance of the push rod 22 and the magnetic scale 23 and limit the circumferential rotation of the push rod 22.

[0036] In this embodiment, the limiting guide structure 3 also includes a roller guide seat 33, which is located in front of the guide limiting seat 32 along the forward direction of the push rod 22, and the push rod 22 passes through the roller guide seat 33.

[0037] The roller guide seat 33 includes an upper roller guide sub-seat and a lower roller guide sub-seat, which are detachably connected. The roller guide seat 33 is used to limit the radial displacement of the push rod 22.

[0038] By adding a roller guide seat 33, which cooperates with the guide limit seat 32, the smooth axial guidance function of the longer push rod 22 can be achieved.

[0039] In this embodiment, the guide limit seat 32 is mounted on the base 31 through a mounting part 34. The guide limit seat 32 and the mounting part 34 are hinged together through a horizontal hinge shaft 35. The horizontal hinge shaft 35 is arranged horizontally and is perpendicular to the axial direction of the push rod 22.

[0040] Practice shows that for tubes with a large length-to-diameter ratio and a large degree of curvature, the push rod 22 may jam. By hingedly connecting the guide limit seat 32 to the base 31 and adding the circumferential limit of the roller guide seat 33, the guide limit seat 32 can rotate at a small angle, further ensuring the smooth axial movement of the push rod 22.

[0041] In this embodiment, the base 31 is provided with a sliding part 36 on the side facing the mounting part 34. The mounting part 34 is slidably connected to the sliding part 36. A fastener 37 is provided between the sliding part 36 and the mounting part 34 to fix the mounting part 34 and the sliding part 36 together.

[0042] In this embodiment, the limiting guide structure 3 also includes a mounting base 38, which is fixed on the base 31 and has a mounting hole 381 that mates with the body tube. One end of the body tube facing the mounting base 38 passes through the mounting hole 381.

[0043] Mounting base 38 is made up of two separate seats that can be detached and connected.

[0044] By designing the limiting guide structure 3 as described above, it is extremely convenient to replace the body tube 6 and disassemble the push rod 22. The push rod 22, magnetic scale 23, guide limit seat 32 and reading head 24 are integrated into one structure, which is convenient for transportation and installation / disassembly.

[0045] In this embodiment, the flexible coupling 4 includes a first connecting member 41, a second connecting member 42, an adapter 43, a first hinge shaft 44, and a second hinge shaft 45. The first connecting member 41 is fixedly connected to the centering structure, and the second connecting member 42 is fixedly connected to the push rod 22. The first connecting member 41 and the adapter 43 are hinged together by the first hinge shaft 44, and the second connecting member 42 and the adapter 43 are hinged together by the second hinge shaft 45. The first hinge shaft 44 and the second hinge shaft 45 are arranged axially perpendicularly.

[0046] Therefore, the push rod 22 can swing at a certain angle in two directions, avoiding the problem of eccentricity during the advancement of the centering structure due to the rigid connection between the push rod 22 and the centering structure, which would affect the measurement accuracy.

[0047] In this embodiment, the laser emitter 1 is mounted on a support base 5, and the support base 5 has a shaft hole 51. The end of the body tube facing the laser emitter 1 passes through the shaft hole 51. The end of the support base 5 facing the laser emitter 1 has an aperture hole 52, and the central axis of the aperture hole 52 coincides with the central axis of the shaft hole 51.

[0048] Specifically, the laser emitter 1 is mounted on the support base 5 via an adjustment mechanism 53, which is used to adjust the light emission position of the laser emitter.

[0049] The adjustment mechanism 53 is a five-axis adjustment mechanism, which can adjust the light output position of the laser emitter in multiple directions.

[0050] A bracket is installed on the end wall of the shaft hole 51 facing the laser emitter 1. An aperture plate is installed at the center of the bracket, and the aperture hole 51 is located at the center of the aperture plate.

[0051] In this embodiment, the centering structure includes a telescopic bushing 25, a fixed bushing 26, a movable bushing 27, and a spring 28. A photoelectric position sensitive detector 21 is installed at one end of the fixed bushing 26, and the other end of the fixed bushing 26 is connected to the push rod 22. The telescopic bushing 25, the movable bushing 27, and the spring 28 are sequentially sleeved on the fixed bushing 26. The outer wall of the telescopic bushing 25 matches the inner wall of the tube, and the telescopic bushing 25 can extend and retract radially under the action of external force. The spring 28 is compressed between the push rod 22 and the movable bushing 27. One end of the inner wall of the telescopic bushing 25 in the axial direction abuts against the fixed bushing 26 through a first wedge structure, and the other end of the inner wall of the telescopic bushing 25 in the axial direction abuts against the movable bushing 27 through a second wedge structure. The first wedge structure and the second wedge structure are arranged symmetrically.

[0052] Therefore, when the centering structure moves along the axial direction of the tube and encounters a decrease in the inner diameter of the tube, the telescopic bushing is compressed and contracts radially to maintain its contact with the inner wall of the tube, and slides backward and downward along the wedge fit, causing the movable bushing to move backward so that the spring is compressed. When the centering structure moves along the axial direction of the tube and encounters an increase in the inner diameter of the tube, the pressure on the telescopic bushing is released and it expands radially. The compressed spring drives the movable bushing to move forward and causes the telescopic bushing to move forward and upward along the wedge fit. The telescopic bushing is compressed between the first wedge structure and the second wedge structure, thus continuing to expand until it maintains its contact with the inner wall of the tube. Therefore, the centering structure can adapt to the radial changes of the tube, thereby obtaining a precise spot position.

[0053] In this embodiment, the telescopic bushing 25 is provided with a plurality of first radial through grooves 251 and a plurality of second radial through grooves 252. The plurality of first radial through grooves 251 and the plurality of second radial through grooves 252 are arranged alternately at intervals along the circumference of the telescopic bushing 25. The first radial through grooves 251 extend axially along the telescopic bushing 25 to penetrate the front end face of the telescopic bushing 25, and the second radial through grooves 252 extend axially along the telescopic bushing 25 to penetrate the rear end face of the telescopic bushing 25.

[0054] The embodiments described above are merely preferred embodiments of this utility model. The terms "in one embodiment," "in another embodiment," "in yet another embodiment," or "in still another embodiment" used in this specification all refer to one or more of the same or different embodiments according to this disclosure. Ordinary variations and substitutions made by those skilled in the art within the scope of this utility model's technical solution should be included within the protection scope of this utility model.

Claims

1. A device for measuring the straightness of a barrel, characterized in that, It includes a laser emitter (1), a measuring structure (2) and a limiting guide structure (3). The laser emitter (1) and the limiting guide structure (3) are respectively located on both sides of the tube in the axial direction. The laser emitter (1) is used to send a laser beam parallel to the tube axis toward the tube. The measuring structure (2) includes a centering mechanism, a photoelectric position sensitive detector (21), a push rod (22), a magnetic scale (23), and a reading head (24). The push rod (22) is mounted on the limiting guide structure (3), which is used to guide and limit the push rod (22) so that the push rod (22) can only move back and forth along its axial direction; the magnetic scale (23) is fixed on the side wall of the push rod (22) and arranged along the axial direction of the push rod (22); the reading head (24) is fixed on the limiting guide structure (3) and is used to sense the grid pitch on the magnetic scale (23); The photoelectric position sensitive detector (21) is located at the end of the centering mechanism facing the laser emitter (1) and is used to detect the position of the spot of the laser beam irradiated on it. The centering mechanism is connected to the end of the push rod (22) facing the laser emitter (1) through the elastic coupling (4) so ​​that the push rod (22) can push the centering mechanism to move back and forth in the tube. The centering mechanism can be arranged coaxially with the tube. The centering mechanism is in cooperation with the inner wall of the tube and can expand and contract in the radial direction under the action of external force to adapt to the radial change of the tube.

2. The tube straightness measuring device according to claim 1, characterized in that, The limiting guide structure (3) includes a base (31) and a guide limiting seat (32) mounted on the base (31). The guide limiting seat (32) has a guide through hole (321) that cooperates with the push rod (22). The guide through hole (321) has a limiting through groove (322) that cooperates with the magnetic scale (23) on the hole wall. The push rod (22) passes through the guide through hole (321), and the magnetic scale (23) passes through the limiting through groove (322). The reading head (24) is mounted on the end of the guide limiting seat (32) facing the magnetic scale (23) through a bracket.

3. The tube straightness measuring device according to claim 2, characterized in that, The limiting guide structure (3) also includes a roller guide seat (33), which is located in front of the guide limiting seat (32) along the forward direction of the push rod (22), and the push rod (22) passes through the roller guide seat (33).

4. The tube straightness measuring device according to claim 3, characterized in that, The guide limit seat (32) is mounted on the base (31) via a mounting part (34). The guide limit seat (32) and the mounting part (34) are hinged together via a horizontal hinge shaft (35). The horizontal hinge shaft (35) is arranged horizontally and is perpendicular to the axial direction of the push rod (22).

5. The tube straightness measuring device according to claim 4, characterized in that, The base (31) has a sliding part (36) on the side facing the mounting part (34). The mounting part (34) and the sliding part (36) are slidably connected. A fastener (37) is provided between the sliding part (36) and the mounting part (34) to fix the mounting part (34) and the sliding part (36).

6. The tube straightness measuring device according to claim 2, characterized in that, The limiting guide structure (3) also includes a mounting base (38), which is fixed on the base (31) and has a mounting hole (381) that mates with the body tube. One end of the body tube facing the mounting base (38) passes through the mounting hole (381).

7. The tube straightness measuring device according to any one of claims 1-6, characterized in that, The flexible coupling (4) includes a first connecting member (41), a second connecting member (42), a transition member (43), a first hinge shaft (44), and a second hinge shaft (45). The first connecting member (41) is fixedly connected to the centering structure, and the second connecting member (42) is fixedly connected to the push rod (22). The first connecting member (41) and the transition member (43) are hinged together through the first hinge shaft (44), and the second connecting member (42) and the transition member (43) are hinged together through the second hinge shaft (45). The first hinge shaft (44) and the second hinge shaft (45) are arranged axially perpendicularly.

8. The tube straightness measuring device according to any one of claims 1-6, characterized in that, The laser emitter (1) is mounted on a support base (5). The support base (5) has a shaft hole (51), and the end of the body tube facing the laser emitter (1) passes through the shaft hole (51). The support base (5) has an aperture hole (52) facing the laser emitter (1), and the central axis of the aperture hole (52) coincides with the central axis of the shaft hole (51).

9. The tube straightness measuring device according to any one of claims 1-6, characterized in that, The centering structure includes a telescopic bushing (25), a fixed bushing (26), a movable bushing (27), and a spring (28). A photoelectric position sensitive detector (21) is installed at one end of the fixed bushing (26), and the other end of the fixed bushing (26) is connected to the push rod (22). The telescopic bushing (25), the movable bushing (27), and the spring (28) are sequentially sleeved on the fixed bushing (26). The outer wall of the telescopic bushing (25) matches the inner wall of the tube, and the telescopic bushing (25) can extend and retract radially under the action of external force. The spring (28) is compressed between the push rod (22) and the movable bushing (27). One end of the inner wall of the telescopic bushing (25) in the axial direction abuts against the fixed bushing (26) through a first wedge structure, and the other end of the inner wall of the telescopic bushing (25) in the axial direction abuts against the movable bushing (27) through a second wedge structure. The first wedge structure and the second wedge structure are arranged symmetrically.

10. The tube straightness measuring device according to claim 9, characterized in that, The telescopic bushing (25) is provided with a plurality of first radial through grooves (251) and a plurality of second radial through grooves (252). The plurality of first radial through grooves (251) and the plurality of second radial through grooves (252) are arranged alternately at intervals along the circumference of the telescopic bushing (25). The first radial through grooves (251) extend axially along the telescopic bushing (25) to penetrate the front end face of the telescopic bushing (25), and the second radial through grooves (252) extend axially along the telescopic bushing (25) to penetrate the rear end face of the telescopic bushing (25).

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