Guide pin defect detection device and method

Abstract

The present invention discloses a guide pin defect detection device and method, which belongs to the technical field of automated detection equipment. The device includes a through gauge with a matching external thread, at least one optical fiber pair and a signal processing unit. Each optical fiber pair consists of an optical fiber output point and a receiving point arranged on the adjacent threads of the through gauge: when the through gauge is screwed in, the optical fiber output point emits a light signal, and in a normal defect-free state, the adjacent thread entity blocks the light path so that the receiving point has no signal; when there is a crack or a fracture in the internal thread, the light signal penetrates the defect and is captured by the receiving point. The signal processing unit determines the defect by analyzing the change in light intensity. Compared with the traditional through gauge that only detects dimensional tolerances, the present invention innovatively combines dynamic optical fiber scanning with thread geometric constraints. During the screwing-in process of the through gauge, a continuous spiral scanning belt is formed, which can identify hidden cracks, improve detection sensitivity, reduce defect missed detection rate, and is compatible with the existing through gauge detection process.

Description

Technical Field

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

[0002] In modern manufacturing, automated inspection equipment is widely used in component quality control to ensure product accuracy and reliability. Existing automated inspection systems typically integrate CCD cameras, image processing algorithms, and a variety of mechanical inspection tools. These systems can quickly identify external burrs on components and verify internal thread dimensions. For example, by employing both go and no-go gauges, internal thread dimensions can be determined to ensure they meet design requirements. After completing both go and no-go gauge inspections, the system typically deems the internal thread dimensions acceptable and determines the test result as acceptable.

[0003] However, even if internal threads meet dimensional requirements, they may still harbor hidden defects such as cracks and fractures, which cannot be detected using traditional go / no-go gaging methods. Because inspection equipment primarily relies on dimensional and appearance parameters to determine thread conformity, the system may mistakenly identify internal threads as conforming even if they contain cracks. Summary of the Invention

[0004] The purpose of the present invention is to provide a guide pin defect detection device, which has the advantage of being able to comprehensively detect axial, spiral directions and micro cracks while improving the detection accuracy, reliability and automation level, thereby improving the quality control level of parts and components and ensuring that the product meets the dimensional requirements while having no potential structural defects.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A guide pin defect detection device, comprising:

[0007] a go gauge having an external thread that matches the internal thread of the guide pin;

[0008] At least one optical fiber pair, each optical fiber pair comprising an optical fiber output point and an optical fiber receiving point, respectively provided on two adjacent threads of the go gauge, wherein the optical fiber output point is configured to emit a detection light signal, and the optical fiber receiving point is configured to be unable to receive the light signal due to the blocked light path when the go gauge is fully screwed into a defect-free internal thread, and to receive the light signal through the crack when a crack is present;

[0009] A signal processing unit is connected to the optical fiber receiving point and is used to determine whether the internal thread has defects based on the received optical signal.

[0010] It is further configured that: the optical fiber output point and the optical fiber receiving point are staggered along the spiral direction of the external thread of the through gauge;

[0011] In which, the optical fiber output point is located at the Nth circle of the external thread of the through gauge, the optical fiber receiving point is located at the N+1th circle, and the axial offset of the optical fiber receiving point relative to the optical fiber output point is one pitch, so that when the through gauge is screwed into the guide pin, the optical path covers the axial extension direction and the spiral extension direction of the internal thread; when there is an axial or spiral crack on the internal thread, the optical signal of the optical fiber output point penetrates the crack to reach the optical fiber receiving point, and triggers defect judgment through the signal processing unit.

[0012] It is further configured that: a plurality of optical fiber pairs are arranged circumferentially in a single thread groove of the through gauge, and the emission direction of each optical fiber pair forms a different angle with the thread axis;

[0013] The multiple fiber pairs include at least:

[0014] The first optical fiber pair has an optical fiber output point and an optical fiber receiving point symmetrically distributed along the radial direction of the thread, and an optical path direction perpendicular to the thread axis;

[0015] The second optical fiber pair has an optical fiber output point and an optical fiber receiving point symmetrically distributed along a 45° clockwise direction;

[0016] The third optical fiber pair has an optical fiber output point and an optical fiber receiving point symmetrically distributed along a 45° counterclockwise direction;

[0017] When there is a crack in any direction on the internal thread, 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 receives the optical signal penetrating the crack and triggers defect judgment through the signal processing unit.

[0018] It is further configured 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;

[0019] The signal processing unit includes a wavelength splitter for separating the mixed optical signal of the optical fiber receiving point according to wavelength, and independently analyzing the light intensity change of each wavelength channel to determine the direction and size of the crack.

[0020] It is further provided that: an aperture is provided between the light source of the optical fiber pair and the optical fiber output point,

[0021] The aperture of the aperture is 0.1-0.5 mm, which is used to limit the divergence angle of light to within ±5°;

[0022] Alternatively, a filter is provided between the light source of the optical fiber pair and the optical fiber output point, and the filter is a bandpass filter with a passband range of 700-1600 nm and a transmittance of less than 1% in the cutoff band outside the passband.

[0023] It is further provided that the installation locations of the optical fiber output point and the optical fiber receiving point on the through gauge are guide holes, and at least a portion of the guide hole is tapered so that the optical fiber end face is lower than the inner thread surface of the through gauge when the optical fiber is inserted.

[0024] Further configuration: the carbon fiber layer or ceramic layer on the surface of the guide hole has a thermal expansion coefficient of less than 2×10 −6 / ℃.

[0025] Further settings: Also includes:

[0026] a rotating mechanism, wherein the through gauge is provided on the rotating mechanism and at least a portion thereof rotates with the rotating mechanism;

[0027] The lifting mechanism, the rotating mechanism is arranged on the lifting mechanism, and is suitable for driving the through gauge to rise and fall.

[0028] Further configuration: the general rule includes:

[0029] A hollow shaft is provided along the axis of the through gauge and has an axial channel formed therein for accommodating the optical fiber;

[0030] An optical fiber slip ring, comprising a rotating end fixedly connected to the hollow shaft and a stationary end connected to the signal processing unit, wherein 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;

[0031] The stationary end remains fixed, and the rotating end of the optical fiber slip ring is transmission-connected to the hollow shaft and the rotating mechanism so that the two rotate synchronously.

[0032] Another object of the present invention is to provide a method for detecting a guide pin defect.

[0033] The following steps are involved:

[0034] S1. Test preparation

[0035] S11. Installing a go gauge: Installing a go gauge having an external thread matching the internal thread of the guide pin into the detection system;

[0036] 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 through gauge are in the correct position and connected to the signal processing unit;

[0037] S13, initializing the light source: starting the optical fiber output point to emit a detection light signal;

[0038] S2. Internal thread detection of guide pin

[0039] S21. Insert the go gauge: screw the go gauge into the internal thread of the guide pin until the go gauge is completely inserted into the internal thread;

[0040] S22, optical signal transmission: During the screwing process of the go gauge, the optical fiber output point continuously emits a detection optical signal;

[0041] S221. When the internal thread of the guide pin is free of defects, the internal thread of the guide pin blocks the optical path, so that the optical fiber receiving point cannot receive the optical signal;

[0042] S222. When there is a crack in the internal thread, the crack allows the detection light signal to penetrate, so that the optical fiber receiving point receives the light signal;

[0043] S3. Signal processing and defect determination

[0044] S31, signal acquisition: the signal processing unit receives the optical signal from the optical fiber receiving point in real time;

[0045] S32, signal analysis: identifying the presence or absence of an optical signal based on the determination of the optical signal by the signal processing unit;

[0046] S321: If the optical fiber receiving point does not receive the optical signal, the internal thread is determined to be in a non-defective state;

[0047] S322: If the optical fiber receiving point receives an optical signal that penetrates the crack, it is determined that there is a defect in the internal thread.

[0048] In summary, the present invention has the following beneficial effects:

[0049] First, traditional through-gauge detection only focuses on whether the size of the internal thread of the inspected part meets the design requirements, and cannot identify hidden defects such as cracks and fractures. In the present invention, optical fiber detection is applied to the through-gauge. During the screw-in process of the through-gauge, a dynamic scanning belt is formed as the thread rotates, which is equivalent to a continuous spiral scan of the thread surface. The optical fiber pair can receive signals to determine defects. While ensuring that the size is qualified, it can detect hidden defects such as cracks and fractures that cannot be identified by traditional detection methods. This method breaks through the traditional detection mode that only relies on size and appearance parameters, improves the comprehensiveness of defect detection, ensures that the internal thread not only meets the size requirements, but also eliminates potential structural defects. In addition, based on the signal transmission principle of optical fiber, this device can accurately judge the changes in optical signals at the optical fiber receiving point, and the optical fiber can sense very small changes in light intensity. This allows the optical fiber pair to detect extremely fine cracks or fractures, thereby improving the accuracy and comprehensiveness of detection.

[0050] Second, in the present invention, by staggering the fiber output point and the fiber receiving point along the helical direction of the external thread of the gauge, the optical path is ensured to cover both the axial and helical directions of the internal thread. This spiral arrangement is particularly suitable for detecting cracks in different directions, particularly cracks in the helical or oblique directions. Due to the misalignment and axial offset of the fiber receiving point and the fiber output point, when a crack exists in the internal thread, the crack allows the light signal to pass through, forming an abnormal signal transmission path. This transmission path makes changes in the detected light signal more pronounced, thereby improving the detection sensitivity.

[0051] Third, in this invention, the fiber pairs can be arranged to cover multiple points along the entire thread. Fiber pairs can be placed in different thread grooves along the longitudinal and helical directions of the thread. By simultaneously detecting multiple fiber pairs at different locations, the fibers can cover a wider area of ​​the thread surface. Even cracks at the thread base or within gaps can be detected through the propagation and refraction of light. This comprehensive coverage ensures that defects are less likely to be missed, especially those deep within the thread.

[0052] Fourth, in the present invention, by providing multiple fiber pairs, the intersection of light paths formed at different angles can mutually verify whether cracks exist. When there is a crack in the internal thread, the light path of at least one group of fiber pairs coincides with or intersects with the direction of crack extension, ensuring that the crack can be detected. Detection can be performed on various complex forms of internal thread defects, especially in cases where the thread morphology is complex or the crack direction is irregular, which 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 direction of the crack and the direction of the light path, cross-verification of multiple groups of fiber pairs can ensure that the defect is detected in a timely manner, thereby improving the reliability of the detection.

[0053] Fifth, in this invention, each fiber pair is assigned an independent wavelength (e.g., 1310nm, 1490nm, 1550nm, 1610nm, etc.), eliminating crosstalk between multiple optical paths through wavelength isolation. The wavelength splitter transmits only the target wavelength (e.g., 1550nm ± 5nm), suppressing interference from workshop lighting (400-700nm) and laser processing stray light (e.g., 1064nm).

[0054] Sixth, in this invention, the original divergence angle of the light source is typically large, resulting in a diffused light spot and reduced energy density. When detecting tiny cracks, an excessively large light spot can result in a weak signal or even an inability to penetrate the crack. By controlling the aperture, the beam's cross-sectional area is physically limited, compressing the divergence angle to within ±5° and forming a collimated light spot with high energy density. This improves detection sensitivity, enabling the identification of even the smallest cracks.

[0055] Seventh, the filter in this invention allows only specific wavelengths (such as infrared) to pass through, suppressing ambient light interference. This reduces metal surface reflectivity and improves penetration. Specifically, infrared wavelengths (such as 1310 / 1550nm) are selected to avoid strong reflections from metal surfaces (visible light reflectivity >80%, infrared reflectivity <30%), thereby improving the signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 Schematic diagram of the structure of the guide pin;

[0057] Figure 2 This is a schematic diagram of the entire guide pin defect detection device;

[0058] Figure 3 This is a schematic diagram of the through gauge detection portion of the guide pin defect detection device;

[0059] Figure 4 yes Figure 3 AA section view in;

[0060] Figure 5 yes Figure 4 A magnified schematic diagram of point B in FIG.

[0061] Figure 6 is a schematic diagram of another embodiment of the rotating mechanism;

[0062] Figure 7 is a schematic diagram of one arrangement of optical fiber pairs;

[0063] Figure 8 is a schematic diagram of the second arrangement of optical fiber pairs;

[0064] Figure 9 is a schematic diagram of the third arrangement of optical fiber pairs;

[0065] Figure 10 This is a schematic diagram of the fourth arrangement of optical fiber pairs.

[0066] In the figure, 100, guide pin; 101, internal thread;

[0067] 200, turntable; 201, workstation; 300, CCD detection module; 400, stop gauge detection module;

[0068] 500, go gauge detection module; 501, hollow shaft; 502, rotating mechanism; 503, lifting mechanism; 504, rotating end; 505, stationary end; 506, optical fiber slip ring; 507, axial channel; 510, go gauge;

[0069] 600, guide hole; 601, optical fiber output point; 602, optical fiber receiving point. DETAILED DESCRIPTION

[0070] The present invention will be further described in detail below with reference to the accompanying drawings.

[0071] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are 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 understood as limiting the present invention.

[0072] A guide pin defect detection device is specifically used to detect defects of the guide pin 100. Figure 1 As shown in FIG, the guide pin 100 structure to be tested is provided with an internal thread 101. 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 through gauge detection module 500, and a stop gauge detection module 400. In some conventional configurations, a labeling module or an NG rejection module or an automatic loading and unloading module may also be added. The present application is an improvement based on the fact that the detection equipment of the prior art is unable to detect the internal thread 101 of the guide pin 100. It is mainly to make further structural changes to the through gauge detection module 500. In this way, the through 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.

[0073] Specifically, this embodiment provides a guide pin defect detection device for detecting defects in 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 effective detection of cracks in the internal thread 101.

[0074] like Figure 3 、 Figure 4 、 Figure 5As shown, the guide pin 100 defect detection device includes a go gauge 510 having an external thread that matches the internal thread 101 of the guide pin 100, at least one optical fiber pair, and a signal processing unit. Matching here means that the pitch of the external thread of the go gauge 510 is consistent with 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 provided on two adjacent threads of the go gauge 510 and arranged relative to each other. The optical fiber output point 601 is configured to emit a detection light 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 obstruction 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 determines the presence of the crack by the change in signal intensity.

[0075] 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. It analyzes the received optical signal intensity in real time to determine whether the internal thread 101 has cracks or other defects. The signal processing unit determines the change in the optical signal based on the set threshold and makes a defect determination. It can also trigger an alarm or provide feedback on the detection results.

[0076] On the basis of the above embodiment, as a further limited embodiment, Figure 3 、 Figure 4 As shown, the process of screwing the go gauge 510 into the guide pin 100 of the present detection device is automatically controlled by the detection equipment, thereby improving the efficiency and stability of the detection. The present detection device further includes a rotating mechanism 502 and a lifting mechanism 503, wherein the go gauge 510 is mounted on the rotating mechanism 502, and at least a portion of the go gauge 510 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 rotate and rise and fall axially, so that the go gauge 510 can maintain a stable feeding state during the process of automatically screwing into the guide pin 100.

[0077] The rotation mechanism 502 is not specifically limited. In this embodiment, it is used to drive the go gauge 510 to rotate about its own axis, allowing it to be smoothly screwed into the internal thread 101 of the guide pin 100 to perform the inspection. The rotation mechanism 502 can be a motor-driven rotary chuck, a gear-driven rotation device, or a magnetic-driven rotation device. The magnetic-driven rotation device can be seen in the schematic diagram of Figure 6.

[0078] 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 lifting mechanism, and a linear guide rail.

[0079] On the basis of the above embodiment, as a further limited embodiment, refer to Figure 3 ,and Figure 4 In this embodiment, the go gauge 510 includes a hollow shaft 501 and a fiber optic slip ring 506 .

[0080] Hollow shaft 501 extends along the axis of go gauge 510, forming an axial channel 507 within it to accommodate the optical fiber, provide protection and guidance for the fiber, and prevent external mechanical interference from affecting its transmission performance. This hollow shaft 501 not only serves as a channel for the optical fiber but also serves as the primary rotation axis of go gauge 510, ensuring that the optical fiber remains in a controlled state during rotation.

[0081] The fiber optic 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 on the outside of the through gauge 510, wherein the output point and receiving point of the optical fiber are arranged at corresponding positions respectively to detect defects in the internal thread 101. Through the optical signal coupling structure of the fiber optic 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 fiber optic slip ring 506 is mechanically connected to the hollow shaft 501 and the rotating mechanism 502. This ensures that when the go gauge 510 rotates, the hollow shaft 501 and the rotating end 504 of the fiber optic slip ring 506 rotate synchronously, preventing the optical fiber from becoming entangled or damaged by stress. Because the stationary end 505 of the fiber optic slip ring 506 is fixed, it ensures stable coupling of the optical signal to the signal processing unit even under high-speed rotation, thereby improving detection reliability and accuracy.

[0082] There is no specific limitation on the arrangement of the optical fiber pairs on adjacent threads. In this embodiment, Figure 7 In the most basic setting, optical fiber pairs on adjacent threads are coaxially positioned relative to each other along the axis of the go gauge 510. This is suitable for detecting radial cracks, i.e., cracks perpendicular to the axis of the go gauge 510. For axial cracks or cracks extending in the helical direction, the optical path may not be able to cover them, resulting in lower detection sensitivity and the possibility of missed detections.

[0083] In this embodiment, reference Figure 8 There is no specific limit on the number of optical fiber pairs arranged on adjacent threads of the through gauge 510 , and the optical fibers can be arranged in multiple groups radially along the through gauge 510 .

[0084] As another preferred embodiment, refer to Figure 9, employing a staggered arrangement along the helical direction of the external thread of the go gauge 510. The fiber output point 601 is located on the Nth turn of the external thread of the go gauge 510, and the fiber receiving point 602 is located on the N+1th turn. The fiber receiving point 602 is offset axially from the fiber output point 601 by a thread pitch p. This arrangement ensures that when the go gauge 510 is screwed into the internal thread 101 of the guide pin 100, the optical paths of the fiber output point 601 and the fiber receiving point 602 overlap along both the axial and helical directions of the thread, enabling detection of defects extending through the thread in different directions.

[0085] During actual testing, when the internal thread 101 of the guide pin 100 is intact, the optical signal is blocked by the external thread and cannot reach the optical fiber receiving point 602. However, if a crack is present in the internal thread 101, regardless of whether the crack propagates axially or helically, the optical signal emitted from the optical fiber output point 601 can pass through the crack and reach the optical fiber receiving point 602. The signal processing unit monitors the changes in the optical signal in real time. When it detects that the optical signal has reached the receiving point, a defect detection is triggered, confirming the presence and location of the crack.

[0086] In this embodiment, reference Figure 9 There is no specific limit on the number of optical fiber pairs arranged on adjacent threads of the through gauge 510 , and optical fibers can be arranged in multiple groups along the spiral direction of the threads of the through gauge 510 .

[0087] In this embodiment, reference Figure 10 There is no specific limit on the number of fiber pairs arranged on adjacent threads of go gauge 510, but three fiber pairs are preferably used. Within a single thread groove of go gauge 510, these three fiber pairs are evenly spaced along the circumference. The emission direction of each fiber pair forms a different angle with the thread axis, covering all directions of the internal thread 101 and ensuring comprehensive crack detection.

[0088] Specifically, the three fiber pairs include at least a first fiber pair, a second fiber pair, and a third fiber pair. The first fiber pair's fiber output point 601 and fiber receiving point 602 are symmetrically distributed along the thread radial direction. Their optical path is perpendicular to the thread axis, forming a radially propagating optical path. This fiber pair is primarily used to detect cracks that extend radially (perpendicular to the thread axis), such as stress cracks caused by turning.

[0089] The second fiber pair's output point 601 and receiving point 602 are symmetrically arranged at a 45° clockwise angle, with their optical path offset at a 45° angle from the thread axis. This fiber pair is effective for detecting cracks tilted in the clockwise direction, particularly right-handed helical cracks and helical cracking caused by bolt preload. The third fiber pair's output point 601 and receiving point 602 are symmetrically arranged at a 45° counterclockwise angle, with their optical path offset at a -45° angle from the thread axis. This fiber pair is primarily used to detect cracks tilted in the counterclockwise direction and identify left-handed helical cracks, such as reverse cracks caused by vibration fatigue.

[0090] The first fiber pair primarily detects axial cracks perpendicular to the thread axis, while the second and third fiber pairs detect cracks in the clockwise and counterclockwise directions, respectively. This ensures that no matter which direction the crack extends, the optical path of at least one fiber pair coincides with or intersects the crack direction. Fiber receiving point 602 receives a light signal that penetrates the crack, triggering crack detection by the signal processing unit. Through this process, the signal processing unit can determine the presence of a crack and perform defect determination based on changes in the received optical signal.

[0091] In tests simulating crack directions of 0°-60°, the missed detection rate decreased from 10% to <1% at a single angle;

[0092] Measure and store the background light intensity (I0) of each fiber pair in a defect-free state. Detect the received light intensity (I) in real time and calculate the relative change ΔI / I0. If ΔI / I0 > 30% (adjustable threshold), it is identified as a crack signal.

[0093] For a crack with a helical angle of 30°, the signal intensities of the three optical paths are:

[0094] 0° optical path: ΔI / I0=15% (partial cross);

[0095] +45° optical path: ΔI / I0=85% (direction coincidence);

[0096] -45° optical path: ΔI / I0=25% (partial cross);

[0097] The alarm is triggered when the threshold is determined (ΔI / I0>30%) and the optical path is at least +45°.

[0098] Based on the above embodiment, as a further limited embodiment, within the multiple fiber pairs, the light source of each fiber pair emits an optical signal of a different wavelength. There is no specific limitation on the signal wavelength of each fiber pair. In this embodiment, the first, second, and third fiber groups are assigned independent wavelengths of 1310nm, 1490nm, and 1550nm. The wavelength interval between each fiber pair is greater than 10nm, such as a wavelength interval of 20nm. By setting optical signals of different wavelengths, it is possible to ensure that the optical signals of each fiber pair do not cross-interfere, and it facilitates signal separation and analysis. Through wavelength isolation, multi-channel signals are separated, solving the crosstalk problem of parallel detection, thereby improving the accuracy and sensitivity of crack detection.

[0099] Based on the above embodiment, as a further limited embodiment, multiple optical fiber alignments are performed, and the signal processing unit includes a wavelength splitter (not shown) that separates the mixed optical signal from the optical fiber receiving point 602 according to wavelength and independently analyzes the intensity changes of each wavelength channel to determine the direction and size of the crack. The wavelength splitter only transmits the target wavelength (e.g., 1550nm±5nm), suppressing interference from workshop lighting (400-700nm) and laser processing stray light (e.g., 1064nm). If a crack is detected only by a single wavelength channel, it may be interference; if the synchronization of multiple wavelength channels is abnormal (e.g., ΔI / I0>30% for both 1310nm and 1550nm), it is confirmed to be a real defect.

[0100] In a further embodiment based on the above, an aperture (not shown) is provided between the light source and the optical fiber output point 601. The aperture has an aperture of 0.1-0.5 mm and is used to limit the light divergence angle to within ±5°. The original divergence angle of the light source is typically large (e.g., ±30°), resulting in a diffuse light spot and reduced energy density. When detecting tiny cracks (e.g., 0.02 mm), an excessively large light spot may result in a weak signal or an inability to penetrate the crack. By limiting the beam cross-sectional area through a physical aperture, the divergence angle is compressed to within ±5°, forming a collimated light spot with high energy density, enabling the detection of even smaller cracks.

[0101] As an alternative embodiment, a filter (not shown in the figure) is provided between the light source and the optical fiber output point 601, wherein: the filter is a bandpass filter with a passband range of 700-1600nm, and the passband selects the infrared band (such as 1310 / 1550nm) to avoid interference from visible light. For example, steel / iron material: the reflectivity in the 1550nm band is less than 30% (visible light > 80%), reducing background noise; aluminum alloy: low infrared absorption rate (better transmittance in 700-900nm), adapted to the filter passband; the transmittance in the cutoff band outside the passband is less than 1%, and the transmittance outside the passband is less than 1%, suppressing 99% of ambient light noise.

[0102] Single-channel signal purification is achieved through the use of apertures / filters, mitigating environmental interference and reflection noise. Apertures / filters are tiny structures located on the fiber endface and are not shown in the figure. They can be installed independently on the fiber endface or integrated with the fiber.

[0103] On the basis of the above embodiment, as a further limited embodiment, Figure 5 As 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 guide hole 600 on the go gauge 510. Among them, at least a portion of the guide hole 600 adopts a tapered design to ensure that when the optical fiber is inserted, the optical fiber end face is located below the surface of the internal thread 101 of the go gauge 510, thereby avoiding contact and friction between the optical fiber and the surface of the internal thread 101, reducing optical fiber damage and signal attenuation that may be caused by friction.

[0104] In addition, the surface of the guide hole 600 is covered with a carbon fiber layer or a ceramic layer, and its thermal expansion coefficient is less than 2×10⁻ 6 / °C, effectively reducing the impact of temperature changes on fiber optic system performance. Carbon fiber and ceramic materials have low thermal expansion coefficients, effectively minimizing the impact of temperature fluctuations on fiber optic installation and signal transmission. Even in environments with large temperature fluctuations, the shape and size of guide hole 600 remain within a minimal range, preventing fiber loosening or optical signal distortion caused by temperature fluctuations, ensuring the stability and accuracy of the fiber optic detection system.

[0105] This embodiment also provides a detection method based on the above-mentioned guide pin defect detection device, comprising the following steps:

[0106] S1. Test preparation

[0107] S11. Installing the go gauge 510: Installing the go gauge 510 having an external thread matching the internal thread 101 of the guide pin 100 into the detection system to ensure that the go gauge 510 can smoothly match the internal thread 101 of the guide pin 100 and enter a working state;

[0108] S12, calibrating the optical fiber pair: ensuring that the optical fiber output point 601 and the optical fiber receiving point 602 provided on two adjacent threads of the through gauge 510 are in the correct position and connected to the signal processing unit;

[0109] S13, initializing the light source: starting the optical fiber output point 601 to emit a detection light signal;

[0110] S2. Detection of the internal thread 101 of the guide pin 100

[0111] S21. Insert the go gauge 510: Insert the go gauge 510 into the internal thread 101 of the guide pin 100 and begin screwing the go gauge 510 into the guide pin 100 until the go gauge 510 completely enters the internal thread 101.

[0112] S22, optical signal transmission: During the process of screwing the go gauge 510 into the guide pin 100, the optical fiber output point 601 continuously emits a detection optical signal;

[0113] S221, when the internal thread 101 of the guide pin 100 is free of 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;

[0114] 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;

[0115] S3. Signal processing and defect determination

[0116] 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 light intensity received by the optical fiber receiving point 602 during the detection process;

[0117] S32, signal analysis: identifying the presence or absence of an optical signal based on the determination of the optical signal by the signal processing unit;

[0118] S321: If the optical fiber receiving point 602 does not receive the optical signal, the internal thread 101 is determined to be in a non-defective state;

[0119] 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.

[0120] A further detection method is provided for the above method, comprising the following steps:

[0121] S1. Test preparation

[0122] S11, installation of 510 standard:

[0123] Install the go gauge 510 to the inspection system, ensuring that it matches the internal thread 101 of the guide pin 100 .

[0124] S12. Calibrate the fiber pair:

[0125] Ensure that the optical fiber output point 601 and the optical fiber receiving point 602 are in the correct position and connected to the signal processing unit.

[0126] S13. Initialize the light source:

[0127] Start the light source and ensure that the optical fiber output point 601 starts to emit the detection light signal.

[0128] S2. Detection of the internal thread 101 of the guide pin 100

[0129] S21, insert the 510 gauge:

[0130] The go gauge 510 is screwed into the internal thread 101 of the guide pin 100 until it completely enters the internal thread 101 .

[0131] S22, Optical signal transmission:

[0132] The optical fiber output point 601 continuously emits an optical signal, and the optical signal is transmitted in real time during the screwing process of the through gauge 510 .

[0133] S221 , non-defective state: the optical signal is completely blocked by the internal thread 101 , and the optical fiber receiving point 602 does not receive any signal.

[0134] S222, crack state: the crack allows light signals to penetrate, and the optical fiber receiving point 602 receives the signal.

[0135] S3. Signal processing and defect determination

[0136] S31, signal acquisition:

[0137] The signal processing unit receives the optical signal from the optical fiber receiving point 602 and calculates the relative change (ΔI / I0).

[0138] S32, Signal Analysis and Judgment:

[0139] The crack is judged by comparing it with the set threshold (for example, ΔI / I0>30%).

[0140] S321 , no defect: If the optical fiber receiving point 602 does not receive the optical signal, it is determined that the internal thread 101 has no defect.

[0141] S322 , crack existence: If a light signal penetrating the crack is received, it is determined that a crack exists in the internal thread 101 .

[0142] S33, Multi-angle and multi-wavelength analysis:

[0143] Independent analysis of cracks in different directions (e.g. 0°, +45°, -45° optical paths) and multi-wavelength optical signals ensures accurate detection and in-depth analysis of various cracks.

[0144] Threshold determination: Based on the ΔI / I0 value of each optical fiber pair, the presence of cracks is determined and an alarm is triggered (e.g., a +45° optical path triggers an alarm).

[0145] S4. Result feedback and alarm

[0146] S41. Data storage and report generation:

[0147] Record crack location, direction, size and other information and generate a test report.

[0148] S42, real-time alarm:

[0149] If the crack signal is found to exceed the threshold, the system will trigger an alarm in time and feedback the detection results for further processing.

[0150] Specific detection cases are given for reference for the above methods.

[0151] Test case 1: Crack detection (thread surface crack)

[0152] Background information: On the surface of the internal thread 101 of a guide pin 100, there is a tiny crack along the axial direction (0° direction). The crack depth is shallow and the direction is completely parallel to the axis of the thread.

[0153] Testing steps:

[0154] S1. Test preparation:

[0155] The go gauge 510 is installed into the detection system and ensured to match the internal thread 101 of the guide pin 100 .

[0156] The optical fiber output point 601 and the receiving point are respectively arranged on two adjacent threads of the through gauge 510 to ensure that the optical fiber is accurately arranged and connected to the signal processing unit.

[0157] The light source is started, and the optical fiber output point 601 begins to emit optical signals.

[0158] S2. Detection of the internal thread 101 of the guide pin 100:

[0159] The go gauge 510 is smoothly screwed into the internal thread 101 of the guide pin 100 .

[0160] The optical fiber output point 601 continuously emits an optical signal and detects changes in the optical signal during the screwing process.

[0161] Since there is a crack on the surface of the internal thread 101 (extending along the 0° direction), the optical signal will pass through the crack and reach the optical fiber receiving point 602 .

[0162] S3. Signal processing and defect determination:

[0163] The signal processing unit receives the optical signal from the optical fiber receiving point 602 and calculates the relative light intensity change (ΔI / I0) in real time.

[0164] 0° optical path: Since the crack extends along the 0° direction, the light signal penetrates the crack location. The calculated result is ΔI / I0 = 15% (the threshold is not reached and the alarm is not triggered).

[0165] +45° optical path: The crack direction partially intersects the optical path, but the optical signal has a strong penetration effect, ΔI / I0 = 25% (does not reach the threshold and does not trigger an alarm).

[0166] -45° optical path: Again, the crack partially intersects the optical path, and the optical signal changes by ΔI / I0 = 10% (does not reach the threshold and does not trigger an alarm).

[0167] S4. Result determination and alarm:

[0168] Since ΔI / I0 did not exceed the set threshold (30%) in all optical paths, the system did not trigger an alarm and determined that the internal thread 101 was free of defects.

[0169] Test case 2: Crack detection (spiral crack)

[0170] Background: A crack exists along the spiral direction (+30°) on the internal thread 101 of a guide pin 100. The crack is deep and has a certain angle with the thread axis.

[0171] Testing steps:

[0172] S1. Test preparation:

[0173] The go gauge 510 is installed in the detection system and matches the internal thread 101 of the guide pin 100 .

[0174] The fiber pairs are aligned and connected to the signal processing unit, ensuring that the output and receiving points of each fiber pair are correctly arranged.

[0175] S2. Detection of the internal thread 101 of the guide pin 100:

[0176] The go gauge 510 begins to be screwed into the internal thread 101 of the guide pin 100 , and the optical fiber output point 601 continues to emit light signals.

[0177] At the crack location, the optical signal will penetrate the crack and be transmitted to the optical fiber receiving point 602, resulting in a significant change in light intensity.

[0178] S3. Signal processing and defect determination:

[0179] The signal processing unit monitors the optical signal changes in real time and calculates the relative change (ΔI / I0).

[0180] 0° optical path: The crack direction does not coincide with the optical path direction of the optical fiber output point 601, ΔI / I0 = 15% (the threshold is not reached, and the alarm is not triggered).

[0181] +45° optical path: The crack direction is close to the optical fiber path, and the optical signal penetrates the crack significantly, with ΔI / I0 = 85% (exceeding the threshold and triggering an alarm).

[0182] -45° optical path: The crack direction partially intersects the optical path, ΔI / I0 = 25% (does not reach the threshold, and does not trigger an alarm).

[0183] S4. Result determination and alarm:

[0184] According to the change in the intensity of the optical signal at the optical fiber receiving point 602, the system triggers an alarm after analysis and marks the direction of the crack as +45°.

[0185] It is determined that there is a crack in the internal thread 101, the crack direction is +45°, and the crack may extend to a deep layer of the internal thread 101.

[0186] Detection Case 3: Multi-wavelength Signal Analysis and Crack Depth Determination

[0187] Background information: There is a deep crack on the internal thread 101 of the guide pin 100. The crack extends along the spiral direction (+30° direction) and is located relatively deep.

[0188] Testing steps:

[0189] S1. Test preparation:

[0190] Configure a multi-wavelength light source and activate optical fiber pairs with different wavelengths for crack detection. Ensure that the signal processing unit can receive and analyze signals at different wavelengths.

[0191] S2. Detection of the internal thread 101 of the guide pin 100:

[0192] The through-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 and transmits them to the optical fiber receiving point 602 .

[0193] S3. Signal processing and defect determination:

[0194] The signal processing unit independently analyzes the optical signals of different wavelength channels.

[0195] Short-wavelength channel: Due to the deep cracks, the short-wavelength optical signal has a weaker penetration effect, ΔI / I0 = 20% (does not exceed the threshold).

[0196] Long wavelength channel: The long wavelength signal has a stronger response to deep cracks, ΔI / I0 = 45% (exceeding the threshold and triggering an alarm).

[0197] S4. Result determination and alarm:

[0198] Through multi-wavelength analysis, the system determines that the crack is a deep crack and triggers an alarm, marking the direction of the crack as +30° and providing crack depth information.

[0199] The above embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the embodiments as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A guide pin defect detection device, characterized in that: include: a go 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 provided 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 the optical signal due to the blocked optical path when the through gauge (510) is completely screwed into the defect-free internal thread (101), and to receive the optical signal through the crack when a crack exists; a signal processing unit connected to the optical fiber receiving point (602) and configured to determine whether the internal thread (101) has a defect based on the received optical signal; The optical fiber output point (601) and the optical fiber receiving point (602) are staggeredly arranged along the helical direction of the external thread of the through gauge (510); The optical fiber output point (601) is located at the Nth turn of the external thread of the through gauge (510), the optical fiber receiving point (602) is located at the N+1th turn, 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.

2. The guide pin defect detection device according to claim 1, characterized in that: Multiple groups of optical fiber pairs are arranged circumferentially in a single thread groove of the through gauge (510), and the emission direction of each group of optical fiber pairs forms a different angle with the thread axis; The multiple fiber pairs include at least: A first optical fiber pair, wherein the optical fiber output point (601) and the 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 tilt of 45°; The third optical fiber pair has an optical fiber output point (601) and an optical fiber receiving point (602) symmetrically distributed along a 45° counterclockwise tilt direction; When a crack in any direction exists on the internal thread (101), the optical path direction of at least one set 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.

3. The guide pin defect detection device according to claim 2, characterized in that: The light sources of each of the multiple fiber pairs emit light signals of different wavelengths, and the wavelength interval between adjacent fiber pairs is greater than 10 nm. The signal processing unit includes 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.

4. The guide pin defect detection device according to claim 2, 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 transmittance of less than 1% in the cutoff band outside the passband.

5. 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 the end face of the optical fiber is lower than the surface of the internal thread (101) of the through gauge (510) when the optical fiber is inserted.

6. The guide pin defect detection device according to claim 5, 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 / ∘C.

7. The guide pin defect detection device according to any one of claims 1 to 6, characterized in that: Also includes: A rotating mechanism (502), wherein the through gauge (510) is provided on the rotating mechanism (502), and at least a portion thereof rotates along with the rotating mechanism (502); The lifting mechanism (503) is provided with the rotating mechanism (502) on the lifting mechanism (503) and is suitable for driving the through gauge (510) to move up and down.

8. The guide pin defect detection device according to claim 7, characterized in that: The general rule (510) includes: A hollow shaft (501) is provided along the axis of the through gauge (510) and has an axial channel (507) formed therein for accommodating an 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 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 realize optical signal coupling with the stationary end (505); The stationary end (505) remains fixed, and the rotating end (504) of the optical fiber slip ring (506) is connected to the hollow shaft (501) and the rotating mechanism (502) in a transmission manner so that the two rotate synchronously.

9. The detection method of the guide pin defect detection device according to any one of claims 1 to 8, 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) provided 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) is free of 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 an 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 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.

Images