A visual inspection device for batch inspection of bearing steel balls

Abstract

This invention relates to the field of bearing steel ball inspection technology, and in particular discloses a visual inspection device for batch inspection of bearing steel balls. The device includes a frame and a feeding mechanism, an electromagnetic levitation channel, and a conveying mechanism arranged sequentially along the conveying direction. The electromagnetic levitation channel is composed of multiple annular electromagnetic coils, with an external diameter adjustment component and internally arranged sequentially along the conveying direction, including an eddy current pre-inspection module, a fiber optic micro-trace detection module, and a visual precision inspection module. A processor is installed on the frame, which fuses eddy current, fiber optic, and visual inspection data to determine surface and subsurface defects of the steel balls, and completes sorting via the conveying mechanism. The advantages are: by employing a multi-level, multi-modal inspection strategy combining eddy current pre-inspection, fiber optic micro-trace detection, and visual precision inspection, it achieves full-dimensional defect detection from subsurface to surface and from macroscopic to microscopic dimensions, significantly reducing the false positive rate and the missed detection rate.

Description

Technical Field

[0001] This invention relates to the field of bearing steel ball testing technology, and in particular to a visual inspection device for batch testing of bearing steel balls. Background Technology

[0002] As the core component of rolling bearings, the surface quality of steel balls (such as pitting, scratches, dents, burns, etc.) directly determines the bearing's vibration noise, precision life, and dynamic performance. With the development of mechanical equipment towards high speed, high precision, and low noise, the performance requirements for bearings and steel balls are becoming increasingly stringent. Consequently, steel ball surface defect detection technology is evolving from manual visual inspection to automation and intelligent processes.

[0003] Currently, steel ball appearance inspection is mainly divided into two categories: mechanical contact unfolding inspection and optical non-contact inspection. For example, patent CN105911064A uses an unfolding disc in conjunction with a vision system, and mechanically limits the steel ball to rotate within a through hole to achieve spherical unfolding. Patent CN117825390A uses a rotating shaft to drive multiple steel balls in the inspection box to roll synchronously, and a CCD camera captures images for inspection. In addition, patent CN118858422B proposes a scheme that uses a coil group to generate a magnetic field to suspend and rotate the steel ball, combined with eddy current testing for inspection.

[0004] Although the aforementioned existing technologies have achieved automation in steel ball detection to some extent, those skilled in the art have found that the existing technologies still have the following technical bottlenecks: Firstly, traditional mechanical roller or conveyor belt conveying methods, as well as mechanical limiting and unfolding methods, are prone to secondary scratches due to rigid contact during the steel ball's entry into the inspection station or unfolding process. For high-precision steel balls (such as G5 grade and above), any minor mechanical collision may cause new defects on their surface, thereby reducing the yield rate.

[0005] Secondly, visual inspection technology alone is insufficient to distinguish between stains, oil films and real micro-scratches on the surface of steel balls, which can easily lead to misjudgment; while eddy current inspection technology alone can effectively detect deep defects such as subsurface cracks and inclusions, it is difficult to intuitively classify and quantify the morphology of shallow surface scratches, which poses a risk of missed detection.

[0006] Third, the channels or fixtures of existing testing equipment are mostly designed with fixed dimensions. When it is necessary to switch to steel balls of different specifications (diameters) for testing, the machine must be stopped and the corresponding tooling fixtures must be replaced. It is impossible to achieve flexible collaborative operation of continuous variable diameter conveying and variable diameter testing, resulting in low testing efficiency and difficulty in adapting to the production needs of multiple varieties and small batches.

[0007] Application content The present invention provides a visual inspection device for batch inspection of bearing steel balls in order to solve the above problems.

[0008] The technical solution of this invention is implemented as follows: A visual inspection device for batch inspection of bearing steel balls includes a frame and a feeding mechanism, an electromagnetic levitation channel, and a conveying mechanism arranged sequentially along the conveying direction. The electromagnetic levitation channel is composed of multiple annular electromagnetic coils arranged axially, and the inner diameter of the annular electromagnetic coils increases or decreases linearly along the conveying direction. A diameter adjustment component is provided on the outside of the electromagnetic levitation channel. An eddy current pre-inspection module is provided at one end of the electromagnetic levitation channel near the feeding mechanism. An optical fiber micro-trace detection module is installed between two adjacent annular electromagnetic coils inside the electromagnetic levitation channel. A visual precision inspection module is installed at one end of the electromagnetic levitation channel near the conveying mechanism. A processor is installed on the frame to receive and process signals from the eddy current pre-inspection module, the optical fiber micro-trace detection module, and the visual precision inspection module.

[0009] Furthermore, the variable diameter adjustment assembly includes a magnetic sleeve sleeved around the periphery of the electromagnetic levitation channel and a first servo motor driving the magnetic sleeve to move axially. A screw and a guide slide rod extending along the axial direction of the electromagnetic levitation channel are disposed outside the channel. The first servo motor is connected to the screw. The magnetic sleeve is fixedly connected to a ball bearing rotatably mounted on the screw. The magnetic sleeve is fixedly connected to a linear bearing slidably mounted on the guide slide rod. By changing the axial displacement of the magnetic sleeve, the effective excitation length of the annular electromagnetic coil is altered, thereby adaptively adjusting the distribution of the magnetic levitation force field generated on the inner wall of the electromagnetic levitation channel, allowing steel balls of different diameters to float stably along the axis and move forward at a uniform speed within the channel.

[0010] Furthermore, the eddy current pre-inspection module employs multi-frequency differential eddy current sensors, which are distributed around the front end of the channel to detect subsurface defects in the steel ball and locate and mark suspected defect areas.

[0011] Furthermore, the fiber optic micro-trace detection module consists of multiple ring-arrayed reflective intensity fiber optic probes, evenly distributed on the same circumferential cross-section of the electromagnetic levitation channel, used to collect reflected light intensity signals from minute defects on the surface of the steel ball (with a minimum resolution of 25μm).

[0012] Furthermore, the visual inspection module includes a fixed base fixed to the end of the electromagnetic levitation channel. A gear sleeve is rotatably mounted in the center of the fixed base. The inner end of the gear sleeve is inserted into the electromagnetic levitation channel and an industrial high-speed camera is fixed to the end. A fixed cylinder, which is also inserted into the inner cavity of the electromagnetic levitation channel, is fixed on the inner wall of the fixed base. Several supplementary light sources are distributed in a ring on the inner wall of the fixed cylinder. A drive mechanism for driving the gear sleeve to rotate is fixed at the end of the electromagnetic levitation channel.

[0013] Furthermore, the drive mechanism includes a driven gear fixed to the outer end of the gear sleeve and a driving gear meshing with it, the driving gear being mounted on the power output shaft of the second servo motor.

[0014] Furthermore, the conveying mechanism includes a receiving guide rail with one end inserted into the inner cavity of the gear sleeve, and the other end of the receiving guide rail is connected to a high-quality guide rail and a low-quality guide rail. A diversion device for controlling the conveying direction of the bearing steel balls is provided at the junction of the high-quality guide rail and the low-quality guide rail.

[0015] Furthermore, the diversion device includes a commutator electrically connected to the processor, and a guide rod that can guide the rolling of bearing steel balls is fixed on the power output shaft of the commutator.

[0016] By adopting the above technical solution, the beneficial effects of the present invention are as follows: This invention achieves dynamic adjustment of the magnetic levitation force field through the synergistic effect of a magnetically conductive sleeve and a ring-shaped electromagnetic coil. This not only eliminates mechanical contact between the steel balls during transport, preventing secondary damage, but also enables adaptive transport of steel balls of different specifications within the same channel, significantly improving the flexibility of the equipment. Simultaneously, by employing a multi-level, multi-modal detection strategy combining eddy current pre-inspection, fiber optic micro-trace detection, and visual precision inspection, it achieves full-dimensional defect detection from subsurface to surface and from macroscopic to microscopic dimensions, greatly reducing the false positive and false negative rates, and providing a reliable technical solution for the batch inspection of high-quality steel balls. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a first perspective view of the present invention; Figure 2 This is a second perspective view of the present invention; Figure 3 This is a main sectional view of the present invention; Figure 4 This is the front view of the present invention; Figure 5 This is a schematic diagram of the installation position of the diversion device of the present invention; Figure 6 This is a schematic diagram of the visual precision inspection module structure of the present invention; Figure 7 This is a circuit structure block diagram of the present invention; Figure 8 This is a flowchart of the steel ball testing process of the present invention.

[0019] The annotations in the attached figures are explained as follows: 1. Frame; 2. Electromagnetic levitation channel; 21. Magnetic insulated shell; 22. Electromagnetic coil; 3. Diameter adjustment assembly; 31. Screw; 32. Guide slide bar; 33. First servo motor; 34. Magnetic sleeve; 4. Feeding mechanism; 5. Conveying mechanism; 51. Receiving guide rail; 52. High-quality guide rail; 53. Defective guide rail; 54. Diverting device; 541. Reversing servo motor; 542. Guide rod; 6. Eddy current pre-inspection module; 7. Fiber optic micro-trace detection module; 8. Visual precision inspection module; 81. Fixed base; 82. Gear sleeve; 83. Driven gear; 84. Fixed cylinder; 85. Complementary light source; 86. Industrial high-speed camera; 87. Second servo motor; 88. Drive gear; 9. Processor; 10. Bearing steel ball. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] like Figures 1-7 As shown, a visual inspection device for batch inspection of bearing steel balls includes a frame 1, and a feeding and conveying mechanism 4, an electromagnetic levitation channel 2, and a conveying mechanism 5, which are sequentially installed on the frame 1 along the conveying direction. The feeding and conveying mechanism 4 is used to guide and convey the bearing steel balls 10 into the electromagnetic levitation channel 2, and the conveying mechanism 5 is used to convey the inspected bearing steel balls 10 into the corresponding storage container.

[0022] The electromagnetic levitation channel 2 consists of a cylindrical, magnetically shielded outer shell 21 and multiple annular electromagnetic coils 22 coaxially arranged inside it. In this embodiment, the magnetically shielded outer shell 21 is made of ceramic, and there are 12 annular electromagnetic coils 22 arranged at equal intervals along the axial direction. Each annular electromagnetic coil 22 is wound with Litz wire to reduce high-frequency eddy current losses, and its inner diameter linearly increases from 50 mm to 100 mm along the conveying direction. This design aims to create a magnetic field gradient that gradually weakens along the conveying direction, providing guiding force for the stable forward movement of the steel ball. When alternating current is applied to the coil, a high-frequency alternating magnetic field is generated in the channel cavity, which in turn induces eddy currents on the surface of the bearing steel ball 10. These eddy currents interact with the external magnetic field to generate a Lorentz force. When the vertically upward component of the Lorentz force balances the gravity of the bearing steel ball 10, the bearing steel ball 10 is in a stable levitation state. By controlling the energizing sequence and current amplitude of each coil, precise control of the levitation height and forward speed of the bearing steel ball 10 can be achieved.

[0023] An adjustable diameter assembly 3 is fitted around the outside of the electromagnetic levitation channel 2. This assembly includes a screw 31 parallel to the channel's axial direction and two guide rods 32, both mounted on the frame 1 via bearing seats. The output shaft of the first servo motor 33 (Panasonic MHMF042L1U2M) is connected to the screw 31 via a coupling. A magnetically conductive sleeve 34, made of high-permeability material (pure iron DT4C), is slidably fitted onto the non-magnetically insulating outer shell 21. The magnetically conductive sleeve 34 is threadedly connected to the screw 31 via ball bearings and slidably connected to the guide rods 32 via linear bearings. When the first servo motor 33 operates, it drives the screw 31 to rotate, thereby causing the magnetically conductive sleeve 34 to move smoothly along the axial direction. When the first servo motor 33 drives the magnetically conductive sleeve 34 to move axially, the magnetic circuit of the coil section covered by the sleeve is bypassed, resulting in a weakening of the magnetic field in that section and an enhancement of the magnetic field in the uncovered section. By dynamically adjusting the length and position of the effective magnetic field zone, the spatial distribution of the electromagnetic levitation force field is matched with the weight and magnetization characteristics of steel balls of different diameters, thereby achieving stable levitation of bearing steel balls 10 of different diameters (such as φ5mm-φ15mm). This enables non-contact diameter adjustment within a closed pipe, avoiding mechanical wear and particulate contamination.

[0024] Inside the electromagnetic levitation channel 2, three detection modules are arranged sequentially along the conveying direction.

[0025] Near the feeding mechanism 4, an eddy current pre-inspection module 6 is installed. In this embodiment, the eddy current pre-inspection module 6 uses three sets of differential eddy current probes, evenly distributed at 45° intervals along the circumference of the channel. The probes are set to operate at three frequency bands: 100kHz, 500kHz, and 1MHz, to detect subsurface defects at different depths. The probes are Olympus Nortec 600 series matching probes.

[0026] In the middle section of the electromagnetic levitation channel 2, a fiber optic micro-trace detection module 7 is installed in the gap between two adjacent annular electromagnetic coils 22. This module consists of eight reflective intensity fiber optic sensors (model FU series from Keyence, Japan). They are precisely embedded on the same circumferential cross section and point at the center of the channel at a 45° angle. The probe uses the ratio method for signal processing to eliminate the influence of light source fluctuations and changes in the curvature radius of the steel ball on the detection accuracy. It has high sensitivity to surface micro-defects larger than 25μm.

[0027] At one end of the electromagnetic levitation channel 2 near the conveying mechanism 5, a visual inspection module 8 is installed. This module includes a fixed base 81 fixedly installed at the end of the electromagnetic levitation channel 2. A gear sleeve 82 is rotatably mounted in the center of the fixed base 81 via a bearing. The inner end of the gear sleeve 82 extends into the inner cavity of the electromagnetic levitation channel 2, and an industrial high-speed camera 86 (model: German Basler acA1300-75gm) is fixed to its inner end with screws. A coaxially arranged fixed cylinder 84 is also fixed on the inner wall of the fixed base 81. The fixed cylinder 84 also extends into the inner cavity of the electromagnetic levitation channel 2 and is located around the industrial high-speed camera 86. Twelve high-brightness LED supplementary light sources 85 (color temperature 5000K, color rendering index >90) are distributed in a ring on the inner wall of the fixed cylinder 84 to provide uniform shadowless illumination for camera shooting.

[0028] The second servo motor 87 (model Mitsubishi HG-KN13J-S100) is fixed on the mounting base 81 or the frame 1. A drive gear 88 is keyed to its output shaft, and the drive gear 88 meshes with the driven gear 83 fixed to the outer end of the gear sleeve 82. When the second servo motor 87 is working, it can drive the gear sleeve 82 and the industrial high-speed camera 86 to rotate around the channel axis, realizing multi-angle imaging of the steel ball surface.

[0029] To achieve precise detection and closed-loop control of the movement position of the bearing steel ball 10 within the electromagnetic levitation channel 2, this equipment also includes a position detection system (not shown in the figure). This system comprises multiple photoelectric sensors spaced at intervals along the axial direction of the electromagnetic levitation channel 2 on the inner wall of the non-magnetic housing 21. Specifically, a set of through-beam infrared photoelectric sensors is installed at the front end of the eddy current pre-inspection module 6, between the eddy current pre-inspection module 6 and the fiber optic micro-trace detection module 7, between the fiber optic micro-trace detection module 7 and the visual precision inspection module 8, and at the rear end of the visual precision inspection module 8. Each set of through-beam infrared photoelectric sensors consists of a transmitter and a receiver, with the transmitter and receiver mounted opposite each other on opposite sides of the inner wall of the non-magnetic housing 21, their optical axis passing through the central axis of the electromagnetic levitation channel 2. When the bearing steel ball 10 levitates and passes through, it blocks the infrared beam, and the receiver outputs a level change signal to the processor 9. The processor 9 calculates the instantaneous position and velocity of the bearing steel ball 10 in real time based on the triggering sequence and interval distance of each photoelectric sensor, and outputs corresponding current amplitude and phase adjustment commands to the ring electromagnetic coil 22 accordingly to achieve closed-loop precise control of the suspension position and forward speed of the bearing steel ball 10. Simultaneously, based on the precise moment when the bearing steel ball 10 enters each detection module, the processor 9 sends synchronous trigger signals to the eddy current pre-inspection module 6, the fiber optic micro-trace detection module 7, and the industrial high-speed camera 86, ensuring that each detection module starts data acquisition when the bearing steel ball 10 reaches the optimal detection position, eliminating the problem of asynchronous detection caused by position errors.

[0030] In another preferred embodiment of the present invention, the conveying mechanism 5 includes a receiving guide rail 51 with one end inserted into the inner cavity of the gear sleeve 82. The receiving guide rail 51 is suspended at a height of no more than 10 mm above the bearing steel ball 10 to smoothly receive the tested steel ball. The receiving guide rail 51 gradually bends downward along the conveying direction to facilitate the automatic outward rolling of the bearing steel ball 10 after it is received. The other end of the receiving guide rail 51 is connected to a forked superior product guide rail 52 and a defective product guide rail 53. A diversion device 54 is provided at the junction of the superior product guide rail 52 and the defective product guide rail 53. The diversion device 54 includes a reversing servo motor 541 (model Futaba S3003) electrically connected to the processor 9. A swingable guide rod 542 is fixed on the power output shaft of the reversing servo motor 541. The processor 9 (which can be an embedded industrial computer based on the ARM Cortex-A9 architecture, such as the MYD-J3358 from MYIR Technology) is mounted on the rack 1 and is connected to the eddy current pre-inspection module 6, the fiber optic micro-trace detection module 7, the industrial high-speed camera 86, the first servo motor 33, the second servo motor 87, and the commutator servo motor 541 respectively. It is used to receive data, analyze and process it, and issue control commands.

[0031] As another preferred embodiment of the present invention, the processor 9 is configured with a modular embedded program that runs on a real-time operating system and adopts a layered architecture design, including a bottom driver layer, an intermediate processing layer and an application decision layer.

[0032] The underlying driver layer includes a sensor data acquisition module and an actuator driver module.

[0033] The sensor data acquisition module is used to receive signals from various sensors, specifically including: three sets of multi-frequency differential eddy current probe signals from the eddy current pre-detection module 6, with a sampling rate set to 100kHz, and three-channel synchronous acquisition using ADC interrupt mode; eight-channel reflective intensity fiber optic sensor signals from the fiber optic micro-trace detection module 7, with a sampling rate set to 50kHz, and eight-channel synchronous acquisition using ADC interrupt mode; five sets of through-beam infrared photoelectric sensor signals arranged at intervals along the axial direction of the electromagnetic levitation channel 2, acquired using GPIO rising edge and falling edge interrupt mode, with an interrupt response time configured to not exceed 10 microseconds; the industrial high-speed camera 86 receives image data through a gigabit Ethernet interface, using an external hardware trigger mode, with the frame rate dynamically adjusted according to the rotation speed of the gear sleeve 82; and the encoder feedback signals of the first servo motor 33 and the second servo motor 87 are acquired through the quadrature encoder interface, with the position closed-loop control frequency configured to 1kHz.

[0034] The actuator drive module is used to output control commands, specifically including: the drive of the ring electromagnetic coil 22 adopts a combination of pulse width modulation and H-bridge circuit, with a control cycle of 500 microseconds, and the current amplitude and phase of each coil can be adjusted independently; the drive of the first servo motor 33 adopts a pulse plus direction signal or bus communication method, with a control cycle of 1 millisecond; the drive of the second servo motor 87 adopts a pulse plus direction signal or bus communication method, with a control cycle of 1 millisecond; the drive of the commutator servo 541 adopts a pulse width modulation signal with a period of 20 milliseconds and a pulse width between 0.5 milliseconds and 2.5 milliseconds.

[0035] The intermediate processing layer includes a steel ball position and velocity calculation module, an electromagnetic levitation closed-loop control module, a detection timing synchronization module, and a data preprocessing module.

[0036] The ball position and velocity calculation module maintains a ball tracking queue, assigning a unique identifier to each bearing ball 10 entering the electromagnetic levitation channel 2. When a photoelectric sensor is triggered, the module records the current timestamp and calculates the instantaneous velocity of the ball in real time using the formula v = L / Δt, based on the fixed distance between adjacent photoelectric sensors and the time difference between their passes, where L is the distance between adjacent photoelectric sensors and Δt is the time difference between adjacent triggers. This module outputs the instantaneous position and velocity of each ball to the electromagnetic levitation control module at an operating frequency of 1kHz.

[0037] The electromagnetic levitation closed-loop control module employs a proportional-integral-derivative (PI-DE) control algorithm. Based on the deviation between the target levitation height and the actual position of the steel ball, it adjusts the current amplitude of the annular electromagnetic coil 22. Its control law is u(t) = Kp·e(t) + Ki·∫e(t)dt + Kd·de(t) / dt, where Kp, Ki, and Kd are the proportional, integral, and derivative coefficients, respectively. These control parameters are set in segments according to the diameter and weight of the steel ball and are synchronously applied when the position of the magnetic sleeve 34 is adjusted via the first servo motor 33. Simultaneously, the module dynamically selects the active coil group based on the current position of the steel ball to achieve smooth movement of the steel ball along the electromagnetic levitation channel 2.

[0038] The timing synchronization module synchronizes the timing of each detection module based on the trigger signal from the photoelectric sensor. When the steel ball passes the front-end photoelectric sensor, the module calculates the delay time based on the real-time calculated speed of the steel ball and the distance between the probe position, and sends trigger signals to start acquisition to the eddy current pre-inspection module 6 and the fiber optic micro-trace detection module 7 after the delay. When the steel ball passes the photoelectric sensor behind the fiber optic detection module, the module sends a hardware trigger signal to the industrial high-speed camera 86 with a delay of no more than 1 millisecond, achieving accurate acquisition of the surface image of the steel ball.

[0039] The data preprocessing module is used to preprocess the raw data collected by each sensor. For eddy current signals, this module performs multi-frequency signal separation, impedance plane analysis, and threshold segmentation, outputting defect presence indicators, defect depth levels, and defect location labels. For fiber optic signals, this module uses the ratio method to calculate reflectivity, performs moving average filtering, and peak detection, outputting the number of reflectivity abrupt change points, abrupt change amplitude, and defect location labels. For image data, this module sequentially performs grayscale conversion, Gaussian filtering, edge detection, and region of interest extraction, outputting defect contour area, aspect ratio, and grayscale contrast features.

[0040] The application decision layer includes a multimodal data fusion module, a defect classification model, and a process flow control state machine.

[0041] The multimodal data fusion module establishes a detection data structure for each steel ball. This structure includes the steel ball's unique number, detection timestamp, diameter specifications, eddy current detection features, fiber optic detection features, visual inspection features, and the final judgment result. The fusion strategy employs a weighted voting mechanism, where the eddy current pre-inspection module 6 has a weight of 0.3, the fiber optic micro-trace detection module 7 has a weight of 0.3, and the visual fine inspection module 8 has a weight of 0.4. When any module detects a serious defect, or when the weighted score reaches or exceeds 0.5, the steel ball is judged as a defective product.

[0042] The defect classification model is configured in the visual fine inspection module 8, employing a lightweight convolutional neural network structure. This network consists of: an input layer receiving a 128×128 pixel grayscale image; a first convolutional layer containing 32 3×3 convolutional kernels using the ReLU activation function, followed by a 2×2 max-pooling layer; a second convolutional layer containing 64 3×3 convolutional kernels using the ReLU activation function, followed by a 2×2 max-pooling layer; a fully connected layer containing 128 neurons with a dropout rate of 0.5; and an output layer using the Softmax activation function, outputting four classification results: no defect, scratches, pits, and dents. The model's parameters are deployed using offline training and online inference, with a single inference time not exceeding 50 milliseconds.

[0043] The process flow control module uses a finite state machine to implement the main control flow. This state machine includes the following states: standby state, waiting for the start command, executing module initialization and sensor reset; parameter setting state, receiving steel ball specification input, controlling the first servo motor 33 to drive the magnetic sleeve 34 to move to the target position; levitation conveying state, starting electromagnetic levitation control after being triggered by the photoelectric sensor, and registering the steel ball identifier; eddy current detection state, collecting eddy current signals and generating features when the steel ball reaches the eddy current probe position; fiber optic detection state, collecting light intensity signals and extracting abrupt change features when the steel ball reaches the fiber optic probe position; visual fine inspection state, triggering the camera to take pictures and running the convolutional neural network classification model when the steel ball reaches the gear sleeve 82; data fusion state, performing weighted fusion to generate the final judgment; sorting execution state, controlling the reversing servo motor 541 to turn according to the judgment result; and reset state, clearing the data of the processed steel balls and waiting for the next steel ball.

[0044] The processor 9 is also equipped with a data recording and communication module, which stores the detection data of each steel ball in CSV format on the local storage medium and generates a new file every day; it communicates with the host computer via Modbus TCP protocol and reports the detection statistics in real time; when the continuous failure rate exceeds the set threshold or the detection module self-test is abnormal, it outputs an audible and visual alarm signal.

[0045] The working principle of this invention is as follows: like Figure 8As shown, before starting the equipment, the operator, based on the specifications of the bearing steel balls 10 to be tested (the specifications of the bearing steel balls 10 to be tested are φ5mm-φ15mm), drives the first servo motor 33 through the control system. The first servo motor 33 drives the screw 31 to rotate, causing the ball sleeve fixed to the magnetic sleeve 34 to move axially along the screw 31. The magnetic sleeve 34 is simultaneously constrained by the guide slide rod 32 to ensure its smooth movement. The change in the position of the magnetic sleeve 34 changes its shielding range on the magnetic circuit of the annular electromagnetic coil 22, that is, it adjusts the effective magnetic force length of the electromagnetic levitation channel 2. After the adjustment is completed, an alternating current is passed into the annular electromagnetic coil 22, generating a gradient magnetic field along the axial direction inside the channel. When the bearing steel balls 10 enter the channel from the feeding mechanism 4, eddy currents are generated inside the steel balls under the action of the alternating magnetic field. These eddy currents interact with the external magnetic field, generating an electromagnetic force opposite to the direction of gravity, making the steel balls stably levitate on the center line of the channel. Because the magnetic force is balanced by the weight of the steel ball, the steel ball will move at a constant speed along the channel axis with the help of a small thrust or magnetic force component at the set suspension height.

[0046] The steel ball first enters the eddy current pre-inspection module 6. This module uses a multi-frequency differential eddy current sensor arranged around the steel ball to apply excitation signals of multiple frequencies. When there are defects such as cracks or inclusions on the surface or subsurface of the steel ball, the distribution of the eddy current field will be disturbed, causing the impedance of the sensor coil to change. By detecting this impedance change, it can be determined whether there are internal or subsurface defects in the steel ball, and a preliminary label of the presence and location of the defect will be generated for the steel ball in the timing record of the processor 9.

[0047] The steel ball continues to move forward and enters the fiber optic micro-scratch detection module 7. This module consists of multiple reflective intensity fiber optic probes evenly distributed on the same circumference. Each fiber optic probe contains both a light-emitting fiber and a light-receiving fiber. The light emitted by the light-emitting fiber illuminates the surface of the high-speed rotating steel ball. When there are pits or tiny scratches on the surface of the steel ball, the intensity of the reflected light at that location will change abruptly. The light-receiving fiber receives the changed light signal, which, after photoelectric conversion and demodulation, generates a characteristic signal reflecting the micro-morphology of the surface and transmits it to the processor 9.

[0048] The steel ball then enters the working area of ​​the visual inspection module 8. After receiving the trigger signal from the front-end eddy current and fiber optic modules, the processor 9 confirms that a steel ball has entered the inspection area and immediately starts the second servo motor 87 and the industrial high-speed camera 86. The second servo motor 87 drives the gear sleeve 82 to rotate through the driving gear 88 and the driven gear 83, thereby causing the industrial high-speed camera 86 to move in a circular motion around the steel ball. At the same time, the supplementary light source 85 on the fixed cylinder 84 provides stable and uniform illumination for the shooting. The industrial high-speed camera 86 performs high-definition image acquisition on the surface of the steel ball from multiple angles, especially the suspected defect areas marked by the preceding module, to obtain precise information such as the shape and size of the defects.

[0049] Processor 9 performs spatiotemporal synchronization and feature fusion of eddy current characteristic signals, fiber optic characteristic signals, and high-definition image features belonging to the same steel ball, and inputs them into a pre-trained classification algorithm model to comprehensively determine whether the steel ball has defects, the type of defects, and their level. When the steel ball moves to the diversion device 54 of the conveying mechanism 5, processor 9 sends a command to the reversing servo motor 541 based on the final judgment result. The reversing servo motor 541 drives the guide rod 542 to rotate to a predetermined angle. If it is determined to be a qualified product, the guide rod 542 guides the steel ball into the superior product guide rail 52; if it is determined to be a defective product, the guide rod 542 guides it into the substandard product guide rail 53, thereby completing the entire detection and sorting process.

[0050] The circuit connection involved in this invention is a conventional method used by those skilled in the art, and technical inspiration can be obtained through a limited number of experiments. It belongs to the widely used prior art.

[0051] Components not described in detail in this article are existing technologies.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A visual inspection device for batch inspection of bearing steel balls, characterized in that: The system includes a frame (1) and a feeding and feeding mechanism (4), an electromagnetic levitation channel (2) and a conveying mechanism (5) arranged sequentially along the conveying direction. The electromagnetic levitation channel (2) is composed of multiple annular electromagnetic coils (22) arranged along the axial direction, and the inner diameter of the annular electromagnetic coils (22) increases or decreases linearly along the conveying direction. A variable diameter adjustment component (3) is provided on the outside of the electromagnetic levitation channel (2). An eddy current pre-inspection module (6) is provided at one end of the electromagnetic levitation channel (2) near the feeding and feeding mechanism (4). An optical fiber micro-trace detection module (7) is installed between two adjacent annular electromagnetic coils (22) inside the electromagnetic levitation channel (2). A visual inspection module (8) is installed at one end of the electromagnetic levitation channel (2) near the conveying mechanism (5). A processor (9) is installed on the frame (1) to receive signals from the eddy current pre-inspection module (6), the optical fiber micro-trace detection module (7) and the visual inspection module (8).

2. The appearance inspection equipment for batch inspection of bearing steel balls according to claim 1, characterized in that: The variable diameter adjustment assembly (3) includes a magnetic sleeve (34) sleeved around the electromagnetic levitation channel (2) and a first servo motor (33) that drives the magnetic sleeve (34) to move axially.

3. The appearance inspection equipment for batch inspection of bearing steel balls according to claim 1, characterized in that: The eddy current pre-detection module (6) uses a multi-frequency differential eddy current sensor, which is distributed around the front end of the channel.

4. The appearance inspection equipment for batch inspection of bearing steel balls according to claim 1, characterized in that: The fiber micro-trace detection module (7) is a reflective intensity fiber probe with multiple ring arrays.

5. The appearance inspection equipment for batch inspection of bearing steel balls according to claim 1, characterized in that: The visual inspection module (8) includes a fixed base (81) fixed at the end of the electromagnetic levitation channel (2). A gear sleeve (82) is rotatably installed in the center of the fixed base (81). The inner end of the gear sleeve (82) is inserted into the electromagnetic levitation channel (2) and an industrial high-speed camera (86) is fixed at the end. A fixed cylinder (84) that is also inserted into the inner cavity of the electromagnetic levitation channel (2) is fixed on the inner wall of the fixed base (81). Several supplementary light sources (85) are distributed in a ring on the inner wall of the fixed cylinder (84). A drive mechanism that drives the gear sleeve (82) to rotate is fixed at the end of the electromagnetic levitation channel (2).

6. The appearance inspection equipment for batch inspection of bearing steel balls according to claim 5, characterized in that: The drive mechanism includes a driven gear (83) fixed to the outer end of the gear sleeve (82) and a driving gear (88) meshing with it. The driving gear (88) is mounted on the power output shaft of the second servo motor (87).

7. The appearance inspection equipment for batch inspection of bearing steel balls according to claim 5, characterized in that: The conveying mechanism (5) includes a receiving guide rail (51) with one end inserted into the inner cavity of the gear sleeve (82), and the other end of the receiving guide rail (51) is connected to a superior guide rail (52) and a defective guide rail (53). A diversion device (54) for controlling the conveying direction of the bearing steel balls (10) is provided at the junction of the superior guide rail (52) and the defective guide rail (53).

8. The appearance inspection equipment for batch inspection of bearing steel balls according to claim 7, characterized in that: The diversion device (54) includes a commutator (541) electrically connected to the processor (9), and a guide rod (542) is fixed on the power output shaft of the commutator (541) to guide the rolling of the bearing steel balls (10).

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