Guide pin defect detection device and method

Abstract

The invention discloses a guide pin defect detection device and method, and belongs to the technical field of automatic detection equipment. The device comprises a go gauge with matched external threads, at least one optical fiber pair and a signal processing unit. Each optical fiber pair is composed of an optical fiber output point and a receiving point which are arranged on adjacent threads of the go gauge: when the go gauge is screwed in, the optical fiber output point emits an optical signal, and in a normal defect-free state, adjacent thread entities block an optical path to make the receiving point have no signal; when the internal thread has a crack or fracture, the optical signal penetrates through the defect and is captured by the receiving point. And the signal processing unit judges the defect by analyzing the light intensity change. Compared with a traditional go gauge which only detects dimensional tolerance, the optical fiber dynamic scanning and the thread geometric constraint are innovatively combined, a continuous spiral scanning band and hidden cracks capable of being recognized are formed in the screwing-in process of the go gauge, the detection sensitivity is improved, the defect omission ratio is reduced, and meanwhile the method is compatible with an existing go gauge detection process.

Description

Technical Field

[0001] The present invention relates to the field of automated detection equipment, and particularly to a guide pin defect detection device and method. Background Art

[0002] In modern manufacturing, automatic detection equipment is widely used in the field of component quality control to ensure the accuracy and reliability of products. Existing automatic detection systems usually integrate CCD cameras, image processing algorithms, and a variety of mechanical detection tools, and can achieve rapid identification of external burrs on components and detection of internal thread dimensions. For example, by using the detection method of a go gauge and a no-go gauge, the dimensions of the internal thread can be determined to ensure that they meet the design requirements. After the go-no-go gauge detection is completed, the system usually considers that the dimensions of the internal thread are in a qualified state, and thus determines the detection result as qualified.

[0003] However, on the premise that the internal thread meets the dimensional requirements, there may be hidden defects such as cracks and fractures, and these defects cannot be identified by traditional go-no-go gauge detection means. Since the detection equipment mainly relies on dimensional and appearance parameters to judge whether the thread is qualified, even if there are crack problems in the internal thread, the system may misjudge it as a qualified state. Summary of the Invention

[0004] The purpose of the present invention is to provide a guide pin defect detection device, which has the advantages of improving detection accuracy, reliability, and automation level, and can comprehensively detect axial, helical directions, and micro-cracks, thereby improving the component quality control level and ensuring that the product has no potential structural defects while meeting the dimensional requirements.

[0005] The above technical purpose of the present invention is achieved through the following technical solutions: A guide pin defect detection device, comprising: A go gauge, which is provided with an external thread matching the internal thread of the guide pin; At least one pair of optical fibers, each pair of optical fibers includes an optical fiber output point and an optical fiber receiving point respectively arranged on two adjacent threads of the go gauge. Among them, the optical fiber output point is configured to emit a detection optical signal, and the optical fiber receiving point is configured to be unable to receive the optical signal due to the blocking of the optical path when the go gauge is fully screwed into a defect-free internal thread, and to receive the optical signal through the crack when there is a crack; A signal processing unit, connected to the optical fiber receiving point, for determining whether there is a defect in the internal thread according to the received optical signal.

[0006] Further setting: The optical fiber output point and the optical fiber receiving point are arranged in a staggered manner along the helix direction of the external thread of the go gauge; Among them, the optical fiber output point is located on the Nth turn of the external thread of the go - gauge, the optical fiber receiving point is located on the (N + 1)th turn, and the axial offset of the optical fiber receiving point relative to the optical fiber output point is one pitch, so that when the go - gauge is screwed into the guide pin, the optical path covers the axial extension direction and the helical extension direction of the internal thread; when there is an axial or helical crack in the internal thread, the optical signal of the optical fiber output point penetrates the crack and reaches the optical fiber receiving point, and the defect determination is triggered through the signal processing unit.

[0007] Further setting: Multiple groups of optical fiber pairs are arranged at intervals circumferentially within a single thread groove of the go - gauge, and the emission directions of each group of optical fiber pairs form different angles with the thread axis; The multiple groups of optical fiber pairs at least include: The first optical fiber pair, whose optical fiber output point and optical fiber receiving point are symmetrically distributed along the radial direction of the thread, and the optical path direction is perpendicular to the thread axis; The second optical fiber pair, whose optical fiber output point and optical fiber receiving point are symmetrically distributed along the direction inclined 45° clockwise; The third optical fiber pair, whose optical fiber output point and optical fiber receiving point are symmetrically distributed along the direction inclined 45° counterclockwise; When there is a crack in any direction in the internal thread, the optical path direction of at least one group of optical fiber pairs coincides with or intersects the crack extension direction, and the optical fiber receiving point receives the optical signal penetrating the crack and triggers the defect determination through the signal processing unit.

[0008] Further setting: The light sources of each group of optical fiber pairs in the multiple groups of optical fiber pairs emit optical signals of different wavelengths, and the wavelength interval between adjacent optical fiber pairs is greater than 10 nm; The signal processing unit includes a demultiplexer, which is used to separate the mixed optical signals of the optical fiber receiving point according to the wavelength, and independently analyze the light intensity changes in each wavelength channel to determine the crack direction and size.

[0009] Further setting: A diaphragm is provided between the light source of the optical fiber pair and the optical fiber output point, The aperture of the diaphragm is 0.1 - 0.5 mm, which is used to limit the divergence angle of light within ±5°; Or, a filter is provided between the light source of the optical fiber pair and the optical fiber output point, the filter is a band - pass filter, and its pass - band range is 700 - 1600 nm, and the transmittance in the cut - off band outside the pass - band is <1%.

[0010] Further setting: The installation positions of the optical fiber output point and the optical fiber receiving point on the go - gauge are guide holes, and at least a part of the guide holes is conical, so that when the optical fiber is inserted, the end face of the optical fiber is lower than the surface of the internal thread of the go - gauge.

[0011] Further setting: The surface of the guide hole is a carbon fiber layer or a ceramic layer, and its coefficient of thermal expansion is less than 2×10 −6 / °C.

[0012] Further settings: It also includes: A rotating mechanism, the go - gauge is arranged on the rotating mechanism, and at least a part rotates with the rotating mechanism; A lifting mechanism, the rotating mechanism is arranged on the lifting mechanism and is adapted to drive the go - gauge to lift.

[0013] Further settings: The go - gauge includes: A hollow shaft, which is arranged through along the axis of the go - gauge, and an axial channel for accommodating an optical fiber is formed inside; An optical fiber slip - ring, including a rotating end fixedly connected to the hollow shaft and a stationary end connected to the signal processing unit. The optical fibers corresponding to the optical fiber output point and the optical fiber receiving point are connected from the rotating end of the hollow shaft to the thread groove of the go - gauge and achieve optical signal coupling with the stationary end; Among them, the stationary end remains fixed, and the rotating end of the optical fiber slip - ring is in transmission connection with the hollow shaft and the rotating mechanism so that the two rotate synchronously.

[0014] Another object of the present invention is to provide a detection method for a guide pin defect detection device, including the following steps: S1. Detection preparation S11. Install the go - gauge: Install the go - gauge with an external thread matching the internal thread of the guide pin into the detection system; S12. Calibrate the optical fiber pair: Ensure that the optical fiber output point and the optical fiber receiving point set on two adjacent threads of the go - gauge are in the correct positions and are connected to the signal processing unit; S13. Initialize the light source: Start the optical fiber output point to emit detection optical signals; S2. Detection of the internal thread of the guide pin S21. Insert the go - gauge: Screw the go - gauge into the internal thread of the guide pin until the go - gauge completely enters the internal thread; S22. Optical signal transmission: During the process of screwing in the go - gauge, the optical fiber output point continuously emits detection optical signals; S221. When there is no defect in the internal thread of the guide pin, the internal thread of the guide pin blocks the optical path, making the optical fiber receiving point unable to receive optical signals; S222. When there is a crack in the internal thread, the crack part allows the detection optical signal to penetrate, resulting in the optical fiber receiving point receiving optical signals; S3. Signal processing and defect determination S31. Signal acquisition: The signal processing unit receives the optical signals from the optical fiber receiving point in real - time; S32. Signal analysis: According to the determination of the optical signals by the signal processing unit, identify the presence or absence of optical signals; S321. If no optical signal is received at the optical fiber receiving point, it is determined that the internal thread is in a defect-free state; S322. If the optical fiber receiving point receives the optical signal penetrating the crack, it is determined that there is a defect in the internal thread.

[0015] In summary, the present invention has the following beneficial effects: First, the traditional go gauge inspection only focuses on whether the size of the internal thread of the part to be inspected meets the design requirements, and cannot identify hidden defects such as cracks and fractures. In the present invention, by applying optical fiber detection to the go gauge, during the process of screwing in the go gauge, a dynamic scanning band is formed along with the rotation of the thread, which is equivalent to continuously helically scanning the thread surface. By using the optical fiber to determine defects based on the received signal, it is possible to detect hidden defects such as cracks and fractures that cannot be identified by traditional detection methods while ensuring that the size is qualified. This method breaks through the traditional detection mode that only relies on size and appearance parameters, improves the comprehensiveness of defect detection, and ensures that the internal thread not only meets the size requirements but also eliminates potential structural defects. Moreover, based on the signal transmission principle of the optical fiber, this device can accurately judge the change of the optical signal at the optical fiber receiving point, and the optical fiber can sense very small changes in light intensity. This enables the optical fiber pair to detect extremely fine cracks or fractures, thereby improving the accuracy and comprehensiveness of detection.

[0016] Second, in the present invention, by arranging the optical fiber output point and the optical fiber receiving point in a staggered manner along the helix direction of the external thread of the go gauge, it is ensured that the direction of the optical path covers the axial and helical directions of the internal thread. This helical arrangement is particularly suitable for detecting cracks in different directions, especially cracks in the helical or inclined directions. Due to the staggered and axially offset settings of the optical fiber receiving point and the optical fiber output point, when there is a crack in the internal thread, the crack allows the optical signal to pass through, forming an abnormal signal transmission path. This transmission path makes the change of the detected optical signal more obvious, thereby improving the detection sensitivity.

[0017] Third, in the present invention, the arrangement of the optical fiber pair can cover multiple points of the entire thread, and the optical fiber pair can be arranged longitudinally and helically along the thread in different thread grooves. Through the synchronous detection of multiple optical fiber pairs at different positions, the optical fiber can cover a larger area of the thread surface. Even cracks at the bottom of the thread or in the gaps can be detected through the propagation and refraction of light. This comprehensiveness of coverage ensures that defects are not easily missed, especially defects deep in the thread.

[0018] Fourth, in the present invention, by providing multiple optical fiber pairs, the optical path intersections formed at different angles can mutually verify the existence of cracks. When there are cracks in the internal thread, the optical paths of at least one group of optical fiber pairs coincide with or cross the crack extension direction, ensuring that the cracks can be detected. It can detect various complex-shaped internal thread defects. Especially in the case of complex thread shapes or irregular crack directions, it can ensure the accuracy of the detection results and effectively reduce the risk of missed detection or misjudgment. Even if there is a certain angle between the crack direction and the optical path direction, the cross-verification of multiple groups of optical fiber pairs can ensure that the defects are detected in a timely manner, thereby improving the reliability of the detection.

[0019] Fifth, in the present invention, each group of optical fiber pairs is assigned an independent wavelength (such as 1310 nm, 1490 nm, 1550 nm, 1610 nm, etc.), and wavelength isolation is used to avoid crosstalk of optical path signals of multiple groups. The demultiplexer only transmits the target wavelength (such as 1550 nm ± 5 nm), suppressing interference such as workshop lighting (400 - 700 nm) and stray light from laser processing (such as 1064 nm).

[0020] Sixth, in the present invention, the original divergence angle of the light source is usually large, resulting in spot diffusion and reduced energy density. When detecting micro-cracks, an overly large spot may result in weak signals or inability to penetrate the cracks. Through the control of the aperture of the diaphragm, the cross-sectional area of the light beam is restricted by a physical aperture, and the divergence angle is compressed to within ±5°, forming a collimated spot with a high energy density. The detection sensitivity is improved, and the minimum crack that can be further identified.

[0021] Seventh, in the present invention, the filter only allows a specific wavelength (such as infrared) to pass through, suppressing environmental light interference. The reflectivity of the metal surface is reduced, and the penetration ability is enhanced. Specifically, for example, the infrared band (such as 1310 / 1550 nm) is selected to avoid strong reflection on the metal surface (visible light reflectivity > 80%, infrared reflectivity < 30%), and the signal-to-noise ratio is improved. Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of the guide pin; Figure 2 is a schematic diagram of the whole machine of the guide pin defect detection device; Figure 3 is a schematic diagram of the go-gauge detection part of the guide pin defect detection device; Figure 4 is Figure 3 the A - A cross-sectional view in Figure 5 is Figure 4 the enlarged view at B in Figure 6 is a schematic diagram of another embodiment of the rotating mechanism; Figure 7It is a schematic diagram of one of the arrangements of the fiber optic pair; Figure 8 It is a schematic diagram of the second arrangement of the fiber optic pair; Figure 9 It is a schematic diagram of the third arrangement of the fiber optic pair; Figure 10 It is a schematic diagram of the fourth arrangement of the fiber optic pair.

[0023] In the figure, 100 is the guide pin; 101 is the internal thread; 200 is the turntable; 201 is the working station; 300 is the ccd detection module; 400 is the go-no-go gauge detection module; 500 is the plug gauge detection module; 501 is the hollow shaft; 502 is the rotating mechanism; 503 is the lifting mechanism; 504 is the rotating end; 505 is the stationary end; 506 is the fiber optic slip ring; 507 is the axial channel; 510 is the plug gauge; 600 is the guide hole; 601 is the fiber optic output point; 602 is the fiber optic receiving point. Detailed implementation mode

[0024] The present invention will be further described in detail below with reference to the accompanying drawings.

[0025] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0026] A guide pin defect detection device is dedicated to detecting the defects of the guide pin 100. As Figure 1 shown, it is the structure of the guide pin 100 to be detected, and the guide pin 100 has an internal thread 101. Refer to Figure 2, in the prior art, a conventional detection device includes a turntable 200 and a plurality of workstations 201 located on the turntable 200. A plurality of detection modules are provided on the circumference of the turntable 200. For example, a ccd detection module 300, a go-gauge detection module 500, and a no-go-gauge detection module 400. In some conventional configurations, a labeling module, an NG rejection module, or an automatic loading and unloading module can also be added. This application is an improvement made based on the fact that the existing detection equipment cannot detect the internal thread 101 of the guide pin 100. Mainly, further structural changes are made to the go-gauge detection module 500. Thus, the go-gauge detection module 500 can not only detect whether the size of the internal thread 101 is qualified, but also simultaneously complete the detection of whether there are cracks on the surface of the internal thread 101.

[0027] Specifically, this embodiment provides a guide pin defect detection device for detecting defects of the internal thread 101, which combines the arrangement of optical fibers along the outer surface of the thread and the transmission characteristics of optical signals to ensure the effective detection of cracks in the internal thread 101.

[0028] As Figure 3 , Figure 4 , Figure 5 shown, the guide pin 100 defect detection device includes a go-gauge 510 having an external thread matching the internal thread 101 of the guide pin 100, at least one optical fiber pair, and a signal processing unit. The matching here means that the pitch of the external thread of the go-gauge 510 is the same as the pitch of the internal thread 101 of the guide pin 100, and the go-gauge 510 is used to be screwed into the internal thread 101 of the guide pin 100. Each optical fiber pair includes an optical fiber output point 601 and an optical fiber receiving point 602. The optical fiber output point 601 and the optical fiber receiving point 602 are respectively arranged on two adjacent threads of the go-gauge 510 and are arranged oppositely. The optical fiber output point 601 is configured to emit a detection optical signal. When the go-gauge 510 is fully screwed into the defect-free internal thread 101, the optical signal cannot be received due to the blocking of the optical path. When there is a crack in the internal thread 101, the crack will allow the optical signal to pass through, so that the optical fiber receiving point 602 receives the optical signal, and the presence of the crack is judged by the change in the signal intensity.

[0029] The signal processing unit is connected to the optical fiber receiving point 602, and is used to receive the optical signal from the optical fiber receiving point 602, and determine whether there are cracks or other defects in the internal thread 101 by analyzing the intensity of the received optical signal in real time. The signal processing unit judges the change of the optical signal and makes a defect determination according to the set threshold, and can trigger an alarm or feedback the detection result at the same time.

[0030] On the basis of the above embodiment, as a further limited embodiment, as Figure 3 , Figure 4As shown, the process of screwing the go - gauge 510 of this inspection device into the guide pin 100 is automatically controlled by the inspection equipment to improve the efficiency and stability of the inspection. This inspection device further includes a rotating mechanism 502 and a lifting mechanism 503. Among them, the go - gauge 510 is installed on the rotating mechanism 502, and at least a part of it can rotate synchronously with the rotating mechanism 502. The rotating mechanism 502 is fixedly arranged above the lifting mechanism 503, and is used to drive the go - gauge 510 to lift axially while rotating, so that the go - gauge 510 can maintain a stable feeding state during the process of automatically screwing into the guide pin 100.

[0031] There is no specific limitation on the rotating mechanism 502. In this embodiment, it is used to drive the go - gauge 510 to rotate around its own axis so that it can be smoothly screwed into the internal thread 101 of the guide pin 100 to achieve the inspection action. The rotating mechanism 502 can adopt a motor - driven rotating chuck, a gear - driven rotating device, or a magnetic - drive rotating device. The magnetic - drive rotating device can refer to the schematic diagram in 6.

[0032] There is no specific limitation on the lifting mechanism 503. In this embodiment, the rotating mechanism 502 is one of an electric push - rod, a linear module, a screw - type lifting mechanism, and a linear guide rail.

[0033] On the basis of the above - mentioned embodiment, as a further - defined embodiment, referring to Figure 3 and Figure 4 , the go - gauge 510 in this embodiment includes a hollow shaft 501 and an optical - fiber slip ring 506.

[0034] The hollow shaft 501 is arranged through along the axis direction of the go - gauge 510, and an axial channel 507 is formed inside it, which is used to accommodate the optical fiber and provide protection and guidance for the optical fiber to prevent external mechanical interference from affecting the optical - fiber transmission performance. This hollow shaft 501 not only serves as an optical - fiber channel but also can be used as the main rotating shaft of the go - gauge 510, so that the optical fiber is always in a controlled state during the rotation process.

[0035] The optical fiber slip ring 506 includes a rotating end 504 and a stationary end 505, wherein: the rotating end 504 is fixedly connected to the hollow shaft 501 and rotates synchronously with the hollow shaft 501; the stationary end 505 is fixedly installed and connected to the signal processing unit to ensure the stability of signal acquisition. The optical fiber is led out from the rotating end 504 of the hollow shaft 501 and connected to the thread groove outside the through gauge 510, wherein the output point and the receiving point of the optical fiber are arranged at corresponding positions respectively, so as to detect the defects of the internal thread 101. Through the optical signal coupling structure of the optical fiber slip ring 506, stable optical signal transmission can be achieved between the rotating end 504 and the stationary end 505, so that even when the through gauge 510 is rotating at high speed, the optical fiber signal can still be reliably transmitted to the signal processing unit without being affected by mechanical rotation. The rotating end 504 of the optical fiber slip ring 506 is connected to the hollow shaft 501 and the rotating mechanism 502 by mechanical connection, so that when the through gauge 510 rotates, the hollow shaft 501 and the rotating end 504 of the optical fiber slip ring 506 always rotate synchronously to avoid the optical fiber from being entangled or damaged by force. Since the stationary end 505 of the optical fiber slip ring 506 is fixed, it can ensure that the optical signal is still stably coupled to the signal processing unit under high-speed rotation conditions, thereby improving the reliability and accuracy of detection.

[0036] There is no specific limitation on the arrangement of the optical fiber pairs on adjacent threads. Figure 7 As the most basic setting, the optical fiber pairs on adjacent threads are coaxially arranged relative to each other along the axis direction of the through gauge 510. It is suitable for radial cracks, that is, cracks perpendicular to the axis of the through gauge 510. For axial cracks or cracks extending in the spiral direction, the optical path sometimes cannot be covered, the detection sensitivity is low, and it may lead to missed detection.

[0037] In this embodiment, reference Figure 8 There is no specific limitation on the number of optical fiber pairs arranged on adjacent threads of the through gauge 510 , and the optical fibers may be arranged in multiple groups radially along the through gauge 510 .

[0038] As another preferred embodiment, refer to Figure 9 , adopting a staggered arrangement along the spiral direction of the external thread of the through gauge 510. Among them, the optical fiber output point 601 is arranged at the Nth circle of the external thread of the through gauge 510, and the optical fiber receiving point 602 is arranged at the N+1th circle, and the offset of the optical fiber receiving point 602 in the axial direction relative to the optical fiber output point 601 is a pitch p. This arrangement ensures that when the through gauge 510 is screwed into the internal thread 101 of the guide pin 100, the optical paths of the optical fiber output point 601 and the optical fiber receiving point 602 are covered along the axial extension direction and the spiral extension direction of the thread, so that defects that pass through different directions of the thread can be detected.

[0039] During the actual detection process, when the internal thread 101 of the guide pin 100 is intact without defects, the optical signal cannot reach the optical fiber receiving point 602 due to the obstruction of the external thread; while when there is a crack in the internal thread 101, regardless of whether the crack propagates along the axial direction or the helical direction, the optical signal emitted from the optical fiber output point 601 may reach the optical fiber receiving point 602 through the crack. The signal processing unit monitors the change of the optical signal in real time. When it detects that the optical signal is transmitted to the receiving point, it can trigger the defect determination, and then confirm the existence and position of the crack.

[0040] In this embodiment, referring to Figure 9 , there is no specific limit on the number of optical fiber pairs arranged on adjacent threads of the go - gauge 510, and multiple groups of optical fibers can be arranged along the helical direction of the threads of the go - gauge 510.

[0041] In this embodiment, referring to Figure 10 , there is no specific limit on the number of optical fiber pairs arranged on adjacent threads of the go - gauge 510, but preferably a layout of three optical fiber pairs is adopted here. Within a single thread groove of the go - gauge 510, these three optical fiber pairs are evenly spaced circumferentially. The emission direction of each optical fiber pair forms a different angle with the thread axis to cover all directions of the internal thread 101 and ensure comprehensive detection of cracks.

[0042] Specifically, the three optical fiber pairs at least include a first optical fiber pair, a second optical fiber pair, and a third optical fiber pair. The optical fiber output point 601 and the optical fiber receiving point 602 of the first optical fiber pair are symmetrically distributed along the radial direction of the thread, and its optical path direction is perpendicular to the thread axis, forming an optical path that propagates radially. This optical fiber pair is mainly used to detect cracks that expand radially (perpendicular to the thread axis), such as turning - machining stress cracks.

[0043] The optical fiber output point 601 and the optical fiber receiving point 602 of the second optical fiber pair are symmetrically distributed along the direction inclined 45° clockwise; its optical path direction is offset by 45° from the thread axis. This optical fiber pair can effectively detect cracks inclined in the clockwise direction, especially capture right - hand helical cracks, such as spiral cracking caused by bolt pre - tightening force. The optical fiber output point 601 and the optical fiber receiving point 602 of the third optical fiber pair are symmetrically distributed along the direction inclined 45° counterclockwise; its optical path direction is offset by - 45° from the thread axis. This optical fiber pair is mainly used to detect cracks inclined in the counterclockwise direction and identify left - hand helical cracks, such as reverse cracks caused by vibration fatigue.

[0044] The first group of optical fiber pairs mainly detects axial cracks perpendicular to the thread axis, while the second and third groups of optical fiber pairs detect cracks in the clockwise and counterclockwise directions respectively, ensuring that no matter in which direction the crack extends, the optical path direction of at least one group of optical fiber pairs coincides with or intersects the crack direction, and the optical signal penetrating the crack is received at the optical fiber receiving point 602, thereby triggering the signal processing unit to detect the crack. Through this process, the signal processing unit can judge the existence of the crack and conduct defect determination according to the change of the received optical signal.

[0045] In the test of simulating the crack direction of 0° - 60°, the missed detection rate ranges from 10% at a single angle to < 1%; Measure and store the background light intensity (I 0 ) of each optical fiber pair in the defect-free state. Detect the received light intensity (I) in real time and calculate the relative change amount ΔI / I 0 . If ΔI / I 0 > 30% (adjustable threshold), it is determined as a crack signal.

[0046] For the crack with a helix angle of 30°, the signal intensities of the three optical paths are as follows: 0° optical path: ΔI / I 0 = 15% (partial intersection); +45° optical path: ΔI / I 0 = 85% (direction coincidence); -45° optical path: ΔI / I 0 = 25% (partial intersection); Through threshold determination (ΔI / I 0 > 30%), at least the +45° optical path triggers an alarm.

[0047] On the basis of the above embodiments, as a further limited embodiment, in multiple groups of optical fiber pairs, the light sources of each group of optical fiber pairs emit optical signals of different wavelengths. There is no specific limitation on the signal wavelength of each optical fiber pair. In this embodiment, the first group of optical fibers, the second group of optical fibers and the third group of optical fibers are assigned independent wavelengths of 1310nm, 1490nm and 1550nm; the wavelength interval of each optical fiber pair is greater than 10nm, such as a wavelength interval of 20nm; by setting optical signals of different wavelengths, it can be ensured that the optical signals of each optical fiber pair will not interfere with each other, and it is helpful to separate and analyze the signals. Through wavelength isolation, multi-channel signals are separated to solve the crosstalk problem of parallel detection, thereby improving the accuracy and sensitivity of crack detection.

[0048] Based on the above embodiments, as a further limited embodiment, among multiple groups of optical fiber pairs, the signal processing unit includes a demultiplexer (not shown in the figure), which is used to separate the mixed optical signals at the optical fiber receiving point 602 according to wavelengths, and independently analyze the optical intensity changes in each wavelength channel to determine the crack direction and size. The demultiplexer only transmits the target wavelength (such as 1550 nm ± 5 nm), and suppresses interference such as workshop lighting (400 - 700 nm) and stray light from laser processing (such as 1064 nm). If a certain crack is only detected by a single wavelength channel, it may be interference; if multiple wavelength channels are synchronously abnormal (such as both 1310 nm and 1550 nm have ΔI / I 0 > 30%), it is confirmed as a real defect.

[0049] Based on the above embodiments, as a further limited embodiment, a diaphragm (not shown in the figure) is provided between the light source and the optical fiber output point 601. The aperture of the diaphragm is 0.1 - 0.5 mm, which is used to limit the divergence angle of light within ±5°; the original divergence angle of the light source is usually large (such as ±30°), resulting in spot diffusion and reduced energy density. When detecting a micro-crack (such as 0.02 mm), an overly large spot may cause weak signals or inability to penetrate the crack. By restricting the cross-sectional area of the light beam through a physical aperture and compressing the divergence angle within ±5°, a collimated spot with a high energy density is formed, enabling smaller cracks to be identified.

[0050] As an alternative embodiment, a filter (not shown in the figure) is provided between the light source and the optical fiber output point 601, where: the filter is a band-pass filter, and its passband range is 700 - 1600 nm. The passband selects the infrared band (such as 1310 / 1550 nm) to avoid visible light interference. For example, for steel / iron materials: the reflectivity in the 1550 nm band is < 30% (visible light > 80%), reducing background noise; for aluminum alloys: the infrared absorption rate is low (the transmittance in the 700 - 900 nm band is better), adapting to the passband of the filter; the transmittance in the cut-off band outside the passband is < 1%, and the transmittance outside the passband is < 1%, suppressing 99% of the ambient light noise.

[0051] Single-channel signal purification is performed through the diaphragm / filter to solve environmental interference and reflection noise. The diaphragm / filter is a micro-structure located on the optical fiber end face, so it is not shown in the figure. It can be independently set at the optical fiber end face or integrated with the optical fiber.

[0052] Based on the above embodiments, as a further limited embodiment, such as Figure 5As shown, in this embodiment, the installation positions of the optical fiber output point 601 and the optical fiber receiving point 602 are set as the guiding holes 600 on the go - gauge 510. Among them, at least a part of the guiding hole 600 is designed in a conical shape to ensure that when the optical fiber is inserted, the end face of the optical fiber is below the surface of the internal thread 101 of the go - gauge 510, thus avoiding contact and friction between the optical fiber and the surface of the internal thread 101, and reducing the possible optical fiber damage and signal attenuation caused by friction.

[0053] In addition, the surface of the guiding hole 600 is covered with a carbon fiber layer or a ceramic layer, and its coefficient of thermal expansion is less than 2×10⁻ 6 / ℃, which can effectively reduce the influence of temperature change on the performance of the optical fiber system. Carbon fiber or ceramic materials have a low coefficient of thermal expansion, which can effectively reduce the influence of temperature fluctuations on optical fiber installation and signal transmission. Even in an environment with large temperature changes, the shape and size changes of the guiding hole 600 will remain within a very small range, avoiding optical fiber loosening or optical signal distortion caused by temperature changes, and ensuring the stability and accuracy of the optical fiber detection system.

[0054] This embodiment also provides a detection method based on the above - mentioned guiding pin defect detection device, including the following steps: S1. Detection preparation S11. Install the go - gauge 510: Install the go - gauge 510 with an external thread matching the internal thread 101 of the guiding pin 100 into the detection system, ensuring that the go - gauge 510 can smoothly cooperate with the internal thread 101 of the guiding pin 100 and enter the working state; S12. Calibrate the optical fiber pair: Ensure that the optical fiber output point 601 and the optical fiber receiving point 602 set on two adjacent threads of the go - gauge 510 are in the correct positions and are connected to the signal processing unit; S13. Initialize the light source: Start the optical fiber output point 601 to emit detection optical signals; S2. Detection of the internal thread 101 of the guiding pin 100 S21. Insert the go - gauge 510: Insert the go - gauge 510 into the internal thread 101 of the guiding pin 100 and start screwing it into the guiding pin 100. The go - gauge 510 should be rotated until it completely enters the internal thread 101; S22. Optical signal transmission: During the process of screwing the go - gauge 510 into the guiding pin 100, the optical fiber output point 601 continuously emits detection optical signals; S221. When there is no defect in the internal thread 101 of the guiding pin 100, the internal thread 101 of the guiding pin 100 blocks the optical path, making the optical fiber receiving point 602 unable to receive optical signals; S222. When there is a crack in the internal thread 101, the crack part allows the detection optical signal to penetrate, causing the optical fiber receiving point 602 to receive optical signals; S3. Signal processing and defect determination S31. Signal acquisition: The signal processing unit receives the optical signal from the optical fiber receiving point 602 in real time; the signal reflects the change in the optical intensity received by the optical fiber receiving point 602 during the detection process. S32. Signal analysis: Identify the presence or absence of the optical signal based on the determination of the optical signal by the signal processing unit. S321. If the optical fiber receiving point 602 does not receive the optical signal, it is determined that the internal thread 101 is in a defect-free state. S322. If the optical fiber receiving point 602 receives the optical signal penetrating the crack, it is determined that the internal thread 101 has a defect.

[0055] The following further detection methods are given for the above method, including the following steps: S1. Detection preparation S11. Install the go gauge 510: Install the go gauge 510 into the detection system to ensure its matching with the internal thread 101 of the guide pin 100.

[0056] S12. Calibrate the optical fiber pair: Ensure that the optical fiber output point 601 and the optical fiber receiving point 602 are in the correct positions and are connected to the signal processing unit.

[0057] S13. Initialize the light source: Start the light source to ensure that the optical fiber output point 601 starts to emit the detection optical signal.

[0058] S2. Detection of the internal thread 101 of the guide pin 100 S21. Insert the go gauge 510: Screw the go gauge 510 into the internal thread 101 of the guide pin 100 until it completely enters the internal thread 101.

[0059] S22. Optical signal transmission: The optical fiber output point 601 continuously emits the optical signal, and the optical signal is transmitted in real time during the process of screwing the go gauge 510.

[0060] S221. Defect-free state: The optical signal is completely blocked by the internal thread 101, and the optical fiber receiving point 602 does not receive the signal.

[0061] S222. Cracked state: The crack part allows the optical signal to penetrate, and the optical fiber receiving point 602 receives the signal.

[0062] S3. Signal processing and defect determination S31. Signal acquisition: The signal processing unit receives the optical signal from the optical fiber receiving point 602 and calculates the relative change amount (ΔI / I 0 ).

[0063] S32. Signal analysis and determination: Compare with the set threshold (e.g., ΔI / I 0 > 30%) to determine cracks.

[0064] S321. No defect: If the optical fiber receiving point 602 does not receive an optical signal, it is determined that the internal thread 101 has no defect.

[0065] S322. Cracks exist: If an optical signal passing through the crack is received, it is determined that the internal thread 101 has cracks.

[0066] S33. Multi-angle and multi-wavelength analysis: Independently analyze cracks in different directions (e.g., 0°, +45°, -45° optical paths) and multi-wavelength optical signals to ensure accurate detection and depth analysis of various cracks.

[0067] Threshold determination: Based on the ΔI / I 0 value of each optical fiber pair, determine the existence of cracks and trigger an alarm (e.g., the +45° optical path triggers an alarm).

[0068] S4. Result feedback and alarm S41. Data storage and report generation: Record information such as the crack location, direction, size, etc., and generate a detection report.

[0069] S42. Real-time alarm: If a crack signal exceeding the threshold is detected, the system promptly triggers an alarm and feeds back the detection result for further processing.

[0070] Provide a specific detection case for the above method for reference.

[0071] Detection case 1: Crack detection (crack on the thread surface) Background information: On the surface of the internal thread 101 of a guide pin 100, there is a small crack along the axial direction (0° direction). The crack depth is relatively shallow and the direction is completely parallel to the axis of the thread.

[0072] Detection steps: S1. Detection preparation: The go gauge 510 is installed in the detection system and ensured to match the internal thread 101 of the guide pin 100.

[0073] The optical fiber output point 601 and the receiving point are respectively set on two adjacent threads of the go gauge 510 to ensure accurate optical fiber arrangement and connection to the signal processing unit.

[0074] Start the light source, and the optical fiber output point 601 starts to emit optical signals.

[0075] S2. Detection of the internal thread 101 of the guide pin 100: The go - gauge 510 is smoothly screwed into the internal thread 101 of the guide pin 100.

[0076] The optical - fiber output point 601 continuously emits optical signals, and the change of the optical signals during the screwing - in process is detected.

[0077] Due to the presence of a crack (extending along the 0° direction) on the surface of the internal thread 101, the optical signal will penetrate at the crack position and reach the optical - fiber receiving point 602.

[0078] S3. Signal processing and defect determination: The signal - processing unit receives the optical signal from the optical - fiber receiving point 602 and calculates the relative optical - intensity change (ΔI / I 0 ) in real - time.

[0079] 0° optical path: Since the crack extends along the 0° direction, the optical signal will penetrate at the crack position, and the calculation result is ΔI / I 0 = 15% (not reaching the threshold, no alarm is triggered).

[0080] +45° optical path: The crack direction has partial intersection with the optical path, but the penetration effect of the optical signal is strong, ΔI / I 0 = 25% (not reaching the threshold, no alarm is triggered).

[0081] -45° optical path: Similarly, the crack has partial intersection with the optical path, and the optical - signal change is ΔI / I 0 = 10% (not reaching the threshold, no alarm is triggered).

[0082] S4. Result determination and alarm: Since ΔI / I 0 does not exceed the set threshold (30%) in all optical paths, the system does not trigger an alarm, and it is determined that the internal thread 101 has no defect.

[0083] Detection case 2: Crack detection (crack in the helical direction) Background information: On the internal thread 101 of a guide pin 100, there is a crack along the helical direction (+30° direction). The depth of the crack is relatively large, and the crack direction has a certain angle with the thread axis.

[0084] Detection steps: S1. Detection preparation: The go - gauge 510 is installed in the detection system and matched with the internal thread 101 of the guide pin 100.

[0085] The optical - fiber pair is calibrated and connected to the signal - processing unit to ensure the correct arrangement of the output point and the receiving point of each optical - fiber pair.

[0086] S2. Detection of the internal thread 101 of the guide pin 100: The go - gauge 510 starts to be screwed into the internal thread 101 of the guide pin 100, and the optical - fiber output point 601 continuously emits optical signals.

[0087] At the crack position, the optical signal will penetrate through the crack and be transmitted to the optical - fiber receiving point 602, resulting in an obvious change in optical intensity.

[0088] S3. Signal processing and defect determination: The signal - processing unit monitors the change of the optical signal in real - time and calculates the relative change amount (ΔI / I 0 ).

[0089] 0° optical path: The crack direction does not coincide with the optical - path direction of the optical - fiber output point 601, ΔI / I 0 = 15% (not reaching the threshold, no alarm is triggered).

[0090] +45° optical path: The crack direction is close to the optical - fiber optical path, and the optical signal penetrates through the crack significantly, ΔI / I 0 = 85% (exceeding the threshold, alarm is triggered).

[0091] - 45° optical path: The crack direction has partial intersection with the optical path, ΔI / I 0 = 25% (not reaching the threshold, no alarm is triggered).

[0092] S4. Result determination and alarm: According to the change of the optical - signal intensity at the optical - fiber receiving point 602, the system triggers an alarm after analysis and marks the crack - occurring direction as the +45° direction.

[0093] It is determined that there is a crack in the internal thread 101, the crack direction is +45°, and the crack may extend to the deep layer of the internal thread 101.

[0094] Detection case 3: Multi - wavelength signal analysis and crack - depth determination Background information: There is a deep crack on the internal thread 101 of the guide pin 100. This crack extends along the spiral direction (+30° direction) and the crack position is relatively deep.

[0095] Detection steps: S1. Detection preparation: Configure a multi - wavelength light source and start the optical - fiber pairs of different wavelengths for crack detection. Ensure that the signal - processing unit can receive signals of different wavelengths respectively and conduct analysis.

[0096] S2. Detection of the internal thread 101 of the guide pin 100: The go - gauge 510 is screwed into the internal thread 101 of the guide pin 100, and the optical - fiber output point 601 emits optical signals of different wavelengths respectively, which are transmitted to the optical - fiber receiving point 602.

[0097] S3. Signal Processing and Defect Judgment: The signal processing unit independently analyzes the optical signals of different wavelength channels.

[0098] Short wavelength channel: Due to the relatively deep crack, the penetration effect of the short wavelength optical signal is weak, and ΔI / I 0 = 20% (not exceeding the threshold).

[0099] Long wavelength channel: The long wavelength signal has a stronger response to deep cracks, and ΔI / I 0 = 45% (exceeding the threshold, triggering an alarm).

[0100] S4. Result Judgment and Alarm: Through multi-wavelength analysis, the system determines that the crack is a deep crack, triggers an alarm, marks the direction of the crack as +30°, and provides crack depth information.

[0101] The above embodiments are only explanations of the present invention, and they do not limit the present invention. After reading this specification, those skilled in the art can make modifications to the embodiments without creative contributions as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A guide pin defect detection device, characterized in that: include: A through gauge (510) having an external thread matching the internal thread (101) of the guide pin (100); At least one optical fiber pair, each optical fiber pair comprising an optical fiber output point (601) and an optical fiber receiving point (602) respectively arranged on two adjacent threads of the through gauge (510), wherein the optical fiber output point (601) is configured to emit a detection optical signal, and the optical fiber receiving point (602) is configured to be unable to receive an optical signal due to the blocked optical path when the through gauge (510) is completely screwed into a defect-free internal thread (101), and to receive an optical signal through the crack when a crack exists; A signal processing unit is connected to the optical fiber receiving point (602) and is used to determine whether the internal thread (101) has a defect based on the received optical signal.

2. The guide pin defect detection device according to claim 1, characterized in that: The optical fiber output point (601) and the optical fiber receiving point (602) are arranged in a staggered manner along the helical direction of the external thread of the through gauge (510); The optical fiber output point (601) is located at the Nth circle of the external thread of the through gauge (510), the optical fiber receiving point (602) is located at the N+1th circle, and the axial offset of the optical fiber receiving point (602) relative to the optical fiber output point (601) is one pitch, so that when the through gauge (510) is screwed into the guide pin (100), the optical path covers the axial extension direction and the spiral extension direction of the internal thread (101); when the internal thread (101) has an axial or spiral crack, the optical signal of the optical fiber output point (601) penetrates the crack to reach the optical fiber receiving point (602), and triggers defect determination through a signal processing unit.

3. The guide pin defect detection device according to claim 1, characterized in that: A plurality of optical fiber pairs are arranged in a circumferentially spaced relationship in a single thread groove of the through gauge (510), and the emission direction of each optical fiber pair forms a different angle with the thread axis; The plurality of optical fiber pairs include at least: A first optical fiber pair, whose optical fiber output point (601) and optical fiber receiving point (602) are symmetrically distributed along the radial direction of the thread, and the optical path direction is perpendicular to the thread axis; The second optical fiber pair has an optical fiber output point (601) and an optical fiber receiving point (602) symmetrically distributed along a clockwise direction tilted at 45°; The third optical fiber pair has an optical fiber output point (601) and an optical fiber receiving point (602) symmetrically distributed along a direction tilted 45° counterclockwise; When a crack in any direction exists on the internal thread (101), the optical path direction of at least one group of optical fiber pairs coincides with or intersects with the crack extension direction, and the optical fiber receiving point (602) receives the optical signal penetrating the crack and triggers defect determination through the signal processing unit.

4. The guide pin defect detection device according to claim 3, characterized in that: The light source of each optical fiber pair in the plurality of optical fiber pairs emits optical signals of different wavelengths, and the wavelength interval between adjacent optical fiber pairs is greater than 10 nm; The signal processing unit comprises a wavelength splitter for separating the mixed optical signal of the optical fiber receiving point (602) according to wavelength, and independently analyzing the light intensity change of each wavelength channel to determine the direction and size of the crack.

5. The guide pin defect detection device according to claim 3, characterized in that: An aperture is provided between the light source of the optical fiber pair and the optical fiber output point (601), wherein the aperture of the aperture is 0.1-0.5 mm and is used to limit the divergence angle of light to within ±5°; Alternatively, a filter is provided between the light source of the optical fiber pair and the optical fiber output point (601), and the filter is a bandpass filter with a passband range of 700-1600nm and a cutoff band transmittance outside the passband of <1%.

6. The guide pin defect detection device according to claim 1, characterized in that: The installation locations of the optical fiber output point (601) and the optical fiber receiving point (602) on the through gauge (510) are guide holes (600), and at least a portion of the guide hole (600) is tapered so that when the optical fiber is inserted, the end face of the optical fiber is lower than the surface of the internal thread (101) of the through gauge (510).

7. The guide pin defect detection device according to claim 6, characterized in that: The carbon fiber layer or ceramic layer on the surface of the guide hole (600) has a thermal expansion coefficient of less than 2×10 −6 / ℃.

8. The guide pin defect detection device according to any one of claims 1 to 7, characterized in that: Also includes: A rotating mechanism (502), wherein the through gauge (510) is disposed on the rotating mechanism (502), and at least a portion thereof rotates along with the rotating mechanism (502); The lifting mechanism (503) is provided on the lifting mechanism (503), and the rotating mechanism (502) is suitable for driving the through gauge (510) to rise and fall.

9. The guide pin defect detection device according to claim 8, characterized in that: The general rule (510) comprises: A hollow shaft (501) is arranged to pass through the axis of the through gauge (510), and an axial channel (507) is formed inside the hollow shaft to accommodate the optical fiber; An optical fiber slip ring (506) comprises a rotating end (504) fixedly connected to the hollow shaft (501) and a stationary end (505) connected to a signal processing unit, wherein the optical fibers corresponding to the optical fiber output point (601) and the optical fiber receiving point (602) are connected from the rotating end (504) of the hollow shaft (501) to the thread groove of the through gauge (510), and optical signal coupling is achieved with the stationary end (505); The stationary end (505) remains fixed, and the rotating end (504) of the optical fiber slip ring (506) is transmission-connected with the hollow shaft (501) and the rotating mechanism (502) so that the two rotate synchronously.

10. The detection method of the guide pin defect detection device according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Test preparation S11, installing a go gauge (510): installing a go gauge (510) having an external thread matching the internal thread (101) of the guide pin (100) in the detection system; S12, calibrating the optical fiber pair: ensuring that the optical fiber output point (601) and the optical fiber receiving point (602) arranged on two adjacent threads of the through gauge (510) are in the correct position and connected to the signal processing unit; S13, initializing the light source: starting the optical fiber output point (601) to emit a detection light signal; S2 Inspection of the internal thread (101) of the guide pin (100) S21, inserting the go gauge (510): screwing the go gauge (510) into the internal thread (101) of the guide pin (100) until the go gauge (510) completely enters the internal thread (101); S22, optical signal transmission: during the screwing process of the through gauge (510), the optical fiber output point (601) continuously emits a detection optical signal; S221, when the internal thread (101) of the guide pin (100) has no defects, the internal thread (101) of the guide pin (100) blocks the optical path, so that the optical fiber receiving point (602) cannot receive the optical signal; S222, when there is a crack in the internal thread (101), the crack allows the detection light signal to penetrate, so that the optical fiber receiving point (602) receives the light signal; S3. Signal processing and defect determination S31, signal acquisition: the signal processing unit receives the optical signal from the optical fiber receiving point (602) in real time; S32, signal analysis: identifying the presence or absence of the optical signal according to the determination of the optical signal by the signal processing unit; S321, if the optical fiber receiving point (602) does not receive the optical signal, it is determined that the internal thread (101) is in a non-defective state; S322. If the optical fiber receiving point (602) receives an optical signal that penetrates the crack, it is determined that the internal thread (101) has a defect.

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