A gear performance testing system based on hybrid metal powder pressing.

Abstract

This invention relates to the field of gear performance testing technology, and more particularly to a gear performance testing system based on mixed metal powder pressing molding, comprising: a testing machine, which includes a rotating component and a support; a defect information acquisition module, including an eddy current probe for acquiring the induced electrical signal generated when the gear under test interacts with an alternating magnetic field and a purging component; a detection module for acquiring the vibration value of the eddy current probe and the dust concentration at a dust concentration sampling point below the eddy current probe; and a control module for determining the current rise slope of the alternating current based on the vibration difference, determining the vertical height of the support based on the overlap between the dust-containing area on the surface of the gear under test during the uniform rotation phase and the corresponding fixed area, and determining the purging duration of the purging component based on the decrease in dust concentration in the dust-containing area within a unit dust monitoring cycle. This invention improves the accuracy of gear performance testing.

Description

Technical Field

[0001] This invention relates to the field of gear performance testing technology, and in particular to a gear performance testing system based on the pressing and molding of mixed metal powder. Background Technology

[0002] Powder metallurgy gears are structural gears manufactured using metal powders, such as iron-based, copper-based, stainless steel, or nickel / cobalt-based alloy powders, through processes including mixing, pressing, sintering, and subsequent shaping. Due to their advantages of minimal cutting, high material utilization, and high mass production efficiency, they are widely used in automotive engine timing pulleys, gearbox synchronizer hubs, motorcycle parts, and household appliance components such as air conditioning compressors. However, due to the characteristics of powder metallurgy processes, a certain proportion of porosity is unavoidable on the interior and surface of the pressed gears, and the density distribution may be uneven. To efficiently detect surface defects such as cracks and inclusions, eddy current testing technology is used because it is non-invasive and non-invasive. With its advantages of fast contact and detection speed and high sensitivity, it has become a commonly used non-destructive testing method in existing technologies. Powder metallurgy gears have microporous structures on their surfaces. In actual eddy current testing, if the excitation frequency generated by the gear acceleration is close to the natural frequency of the internal components of the probe, it is easy to induce a resonance response. This leads to fretting wear at the contact interface of components with different material densities, causing local thinning of the coil insulation layer. Insulation degradation will cause abnormal charge accumulation and local polarization under the alternating electric field, which in turn attracts environmental dust to be directionally adsorbed below the probe, changing the electromagnetic coupling state and causing eddy current signal baseline drift and defect misjudgment. Therefore, there is an urgent need for a gear performance testing system that addresses the characteristics of charge trapping and dust adsorption in the micropores on the surface of powder metallurgy gears.

[0003] Chinese Patent Publication No. CN120539264A discloses a gear defect detection system and method based on gear pump processing. The system includes a gear defect detection platform, which is communicatively connected to a magnetization preprocessing module, a magnetic signal acquisition module, a magnetic signal processing module, a gear defect analysis module, and a defect visualization and annotation module. These modules are electrically connected. The magnetization preprocessing module is used to customize a magnetization scheme based on the material and structural characteristics of the gear. This invention employs signal separation and feature extraction techniques to effectively extract independent features of different defect types from the magnetic signal and construct a defect classification model. This allows for accurate differentiation of surface damage, geometric deformation, and fatigue cracks, and quantitative analysis of the severity of defects. However, the gear defect detection system and method based on gear pump processing suffer from a problem: when detecting defects on the gear surface using an alternating magnetic field, the accelerated rotation of the gear causes fretting wear at the contact interfaces of components with different material densities inside the probe. This thins the insulation layer of the coil windings at the contact interfaces, leading to dust adsorption on the gear surface through additional electrostatic discharge. This reduces the accuracy of detecting surface defects through the eddy current effect. Summary of the Invention

[0004] To address this issue, the present invention provides a gear performance testing system based on mixed metal powder pressing molding, which overcomes the problem in the prior art where, when detecting defects on the surface of a gear by generating an alternating magnetic field, the accelerated rotation of the gear causes fretting wear at the contact interface of components with different material densities inside the probe, resulting in thinning of the insulation layer of the coil winding at the contact interface. This leads to the adsorption of dust on the surface of the gear by additional electrostatic charge, thus reducing the accuracy of detecting surface defects of the gear through the eddy current effect.

[0005] To achieve the above objectives, the present invention provides a gear performance testing system based on mixed metal powder pressing molding, comprising: The testing machine includes a rotating assembly for fixing and driving the gear to be tested, which is formed by pressing mixed metal powder, to rotate, and a bracket for limiting the testing height of the gear to be tested. The defect information acquisition module is connected to the testing machine and is used to acquire surface defect information of the gear under test. It includes an eddy current probe set above the gear under test to apply an alternating magnetic field to the gear under test to acquire the induced electrical signal generated when the gear under test interacts with the alternating magnetic field, and a purging assembly set on a bracket near the eddy current probe. The detection module is connected to the defect information acquisition module to obtain the vibration value of the eddy current probe and the dust concentration at the dust concentration sampling point below the eddy current probe. The control module, which is connected to the defect information acquisition module and the detection module respectively, is used to determine the current rise slope of the AC current based on the vibration difference of the gear under test during the accelerated rotation phase, determine the vertical height of the bracket based on the overlap between the dust presence area on the surface of the gear under test and the corresponding fixed part area during the uniform rotation phase, and determine the purging duration of the purging assembly based on the decrease in dust concentration in the dust presence area within a unit dust monitoring cycle.

[0006] Furthermore, the internal enclosure of the eddy current probe includes a coil for generating an alternating magnetic field through alternating current, a magnetic core for defining the effective area of ​​the alternating magnetic field, and a fixing part filled between the coil, the magnetic core, and the outer shell of the eddy current probe for insulation, fixing, and protection.

[0007] Furthermore, the detection module includes: A vibration sensor, connected to the bracket, is used to acquire the vibration value of the eddy current probe; A dust concentration sensor array, which is horizontally arranged at equal intervals around the eddy current probe, is used to obtain the dust concentration at the dust concentration sampling point below the eddy current probe.

[0008] Furthermore, the dust-containing area is the largest area enclosed by all dust concentration sampling points on the surface of the gear under test whose dust concentration is greater than a preset concentration. The corresponding fixed part area is the three-dimensional area occupied by the annular gap space formed between the single-turn coil and the surface of the magnetic core in the fixed part inside the housing of the eddy current probe.

[0009] Furthermore, the control module is used to determine, based on the comparison result that the vibration difference of the gear under test during the accelerated rotation phase is greater than a preset difference, whether the wear degree of the contact interface of each component internally encapsulated in the eddy current probe does not meet the requirements, and to reduce the current rise slope of the alternating current. The current rise slope of the alternating current is negatively correlated with the vibration difference. The vibration difference is the difference between the vibration value at the eddy current probe and the preset vibration reference value of the gear under test during the accelerated rotation phase.

[0010] Furthermore, the control module is used to determine, based on the judgment result that the overlap between the dust-existing area and the corresponding fixed part area is greater than a preset overlap, the degree of influence of the environmental dust attracted by the leakage static electricity into the detection gap causing the surface defect detection of the gear under test does not meet the requirements, and to increase the vertical height of the bracket.

[0011] Furthermore, the vertical height of the support is positively correlated with the degree of overlap, wherein, The overlap is the ratio of the projected area of ​​the corresponding fixed part region on the dust-existing area to the area of ​​the dust-existing area. The vertical height of the bracket is the shortest vertical distance between the bracket and the gear to be tested.

[0012] Furthermore, the control module is used to determine, based on the judgment result that the decrease in dust concentration in the dust-existing area within a unit dust monitoring cycle is greater than a preset decrease, that the dust adsorbed by the trapped charge on the surface of the gear under test does not meet the requirements for the degree of contamination of the eddy current probe surface, and to extend the purging time of the purging assembly.

[0013] Furthermore, the reduction in dust concentration is the difference between the dust concentration at the beginning and the end of the dust presence area within a unit dust monitoring cycle.

[0014] Furthermore, the purging duration is positively correlated with the reduction in dust concentration.

[0015] Compared with the prior art, the beneficial effect of the present invention is that, by setting the current rise slope of the alternating current based on the difference between the vibration value at the eddy current probe of the gear under test during the accelerated rotation phase and a preset vibration reference value, the present invention reduces the instantaneous dielectric stress in the area where the insulation layer is thinned under the action of high-frequency alternating current. This reduces the risk and scope of insulation layer breakdown due to thinning, thus overcoming the problem that vibration generated during the gear's accelerated rotation is transmitted to the eddy current probe, causing fretting wear between the components inside the eddy current probe, resulting in thinning of the insulation layer of the coil winding below the contact interface. This significantly increases the risk of insulation layer breakdown during subsequent high-frequency alternating current eddy current testing. This causes some of the internal charge to escape to the thinner outer surface of the insulation layer. This makes the charge on the thinner outer surface of the insulation layer more susceptible to attracting dust from the air, thus reducing the actual distance between the thinner insulation layer surface and the eddy current probe, leading to detection errors. Specifically, when the gear accelerates, the vibration generated by this acceleration is transmitted to the eddy current probe through the testing machine and support. When the excitation frequency of the vibration transmitted by the support approaches the natural frequency of the components encapsulated inside the eddy current probe during acceleration, it triggers a resonant response in the internal components. Because the material densities of the various components inside the eddy current probe—namely, the coil, magnetic core, and fixing part—are different, this leads to… When vibration occurs, the inertial forces generated by each component differ, causing resonance to amplify the relative displacement between components. This leads to shear stress and fretting wear at the contact interfaces of the components. Fretting wear thins the insulation layer of the coil windings below the contact interface. When a high-frequency alternating current is applied for eddy current testing, the thinned insulation layer accelerates electrical aging. Under the same current, the electric field strength inside and on the surface of the electrically aged insulation layer increases. When the electric field strength approaches the dielectric breakdown threshold of the insulation layer, local polarization occurs on the surface of the insulation layer. This local polarization causes the bound charges inside the insulation material to gain sufficient energy, detach from their original atomic or molecular orbitals, and transform into molecules that can migrate in the air. Free charge carriers migrate towards the electrically aged insulation layer under the electric field of alternating current, and are captured during the migration, unable to continue conducting. The captured charge accumulates at the interface, and the dust adsorbed by the accumulated charge forms a non-conductive layer of uneven thickness between the probe and the surface of the gear under test. This results in the actual detection distance being smaller than the standard detection distance, causing a deviation in the measurement of defect depth. Therefore, by reducing the current rise slope of the alternating current, the instantaneous dielectric stress in the thinned area of ​​the insulation layer under the electric field of high-frequency alternating current is reduced, avoiding the accelerated local electrical aging of the insulation layer, weakening the attraction of charge to dust in the air, and further improving the accuracy of the gear performance testing system.

[0016] Furthermore, this invention increases the vertical height of the support by increasing the overlap between the dust-containing area and the corresponding fixed area of ​​the gear under test during uniform rotation, thereby reducing dust below the eddy current probe, avoiding signal shielding and eddy current path distortion caused by conductive dust, restoring the effective penetration capability of the alternating magnetic field on the surface of the gear under test, and ensuring the signal-to-noise ratio and spatial resolution of the surface defect acquisition of the gear under test. This overcomes the problem that dust below the eddy current probe, after being polarized in the electric field, is more easily attracted by electrostatic force and accumulates under the thinned insulation layer due to wear. This is because the gear under test enters... After the uniform rotation stage, the rotational speed of the gear under test tends to stabilize, and the inertial disturbance of dust particles is weakened. At this time, electrostatic adsorption force and gravitational settling become the dominant forces. The dust migrates along the electric field gradient direction and accumulates in the projection area directly below the fixed part between the coil and the magnetic core, that is, the projection area directly below the corresponding fixed part area. The higher the overlap, the stronger the spatial coupling between the electrostatic adsorption field source and the detection area of ​​the alternating magnetic field below the eddy current probe. This also increases the degree of interference of the eddy current signal by dust shielding and path distortion, further improving the accuracy of the gear performance testing system.

[0017] Furthermore, based on the judgment that the decrease in dust concentration in the dust-existing area within a unit dust monitoring cycle is greater than a preset decrease, the present invention extends the purging time of the purging component. This utilizes airflow pressure to overcome the electrostatic adsorption force between dust particles and the probe surface, allowing the attached dust to gain sufficient kinetic energy to detach from the surface and be discharged with the airflow. This physically removes the dust contamination layer, restores the initial detection gap between the eddy current probe and the gear under test, and ensures the stability of alternating magnetic field energy transmission. This overcomes the tendency of the electrostatic attraction of the insulation layer due to localized electro-aging to reach the surface of the eddy current probe. The electric field on the surface of the eddy current probe polarizes the dust, enhancing the attraction between the dust and the eddy current probe. At this point, electrostatic force becomes the dominant adsorption force for dust particles, and the adsorption force of electrostatic force on dust is far greater. Due to the gravity of the dust itself, the captured dust particles are difficult to fall off by gravity or natural airflow, thus remaining on the surface of the eddy current probe. If dust is present on the surface of the eddy current probe, it will increase the background noise of the induced electrical signal received from the surface of the gear under test, which will lead to false sheet defects when detecting surface defects of the gear under test, resulting in a decrease in the accuracy of gear performance testing. The decrease in dust concentration in the dust-containing area within a unit dust monitoring cycle represents the amount of dust falling off the surface of the gear under test. When the decrease in dust concentration representing the amount of dust falling off is greater than the preset decrease, it indicates that the concentration in the dust-containing area is decreasing. The above measures improve the accuracy of performance testing of gears formed by pressing mixed metal powder. Attached Figure Description

[0018] Figure 1This is a structural block diagram of a gear performance testing system based on the pressing and molding of mixed metal powder, according to an embodiment of the present invention. Figure 2 This is a structural block diagram of the defect information acquisition module of the gear performance testing system based on mixed metal powder pressing molding according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the eddy current probe and the gear under test in the gear performance testing system based on the pressing of mixed metal powder according to an embodiment of the present invention. Figure 4 This is a logic block diagram for determining the current rise slope of alternating current in a gear performance testing system based on mixed metal powder pressing, according to an embodiment of the present invention. Figure 5 This is a schematic diagram of the structure of the fixed part region of the gear performance testing system based on the pressing of mixed metal powder in the dust presence region according to an embodiment of the present invention. Explanation of reference numerals in the attached drawings: 1-Eddy current probe, 2-Air nozzle, 3-Detection platform, 4-Limiting cylinder, 5-Bracket, 6-Rotating shaft, 7-Shaft seat, 8-Motor, 9-Dust concentration sampling point, 10-Vibration sensor, 11-Limiting block, 12-Coil, 13-Magnetic core, 14-Surface of the gear to be tested, 15-Corresponding fixed area, 16-Dust presence area, 17-Outer shell. Detailed Implementation

[0019] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0021] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0022] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Please see Figure 1 , Figure 2 as well as Figure 3 The diagrams shown are, respectively, a structural block diagram of the gear performance testing system based on mixed metal powder pressing molding, a structural block diagram of the defect information acquisition module, and a structural schematic diagram of the eddy current probe and the gear under test according to an embodiment of the present invention; the gear performance testing system based on mixed metal powder pressing molding according to an embodiment of the present invention includes: The testing machine 3 includes a rotating assembly for fixing and driving the gear to be tested, which is formed by pressing mixed metal powder, to rotate, and a bracket 5 for limiting the testing height of the gear to be tested. The defect information acquisition module is connected to the testing machine 3 and is used to acquire surface defect information of the gear under test. It includes an eddy current probe 1 set above the gear under test to apply an alternating magnetic field to the gear under test to acquire the induced electrical signal generated when the gear under test interacts with the alternating magnetic field, and a purging assembly set on a bracket near the eddy current probe. The detection module is connected to the defect information acquisition module to obtain the vibration value of the eddy current probe and the dust concentration at the dust concentration sampling point below the eddy current probe. The control module, which is connected to the defect information acquisition module and the detection module respectively, is used to determine the current rise slope of the AC current based on the vibration difference of the gear under test during the accelerated rotation phase, determine the vertical height of the bracket based on the overlap between the dust presence area on the surface of the gear under test and the corresponding fixed part area during the uniform rotation phase, and determine the purging duration of the purging assembly based on the decrease in dust concentration in the dust presence area within a unit dust monitoring cycle.

[0024] Specifically, in this embodiment of the invention, the gear to be tested is preferably a gear formed by pressing together a mixture of iron, copper and carbon powder in a mass ratio of 1:2:0.8; the gear to be tested has a module of 2.5, 24 teeth, and a tooth surface roughness of 0.8±0.1μm.

[0025] Those skilled in the art will understand that the gear under test is a gear formed by pressing mixed metal powder. There is no limitation on the type of gear under test. Those skilled in the art can make adaptive adjustments to the type of gear under test according to the actual application or testing requirements.

[0026] Specifically, the rotating assembly includes a limiting cylinder 4 sleeved on the outer circumference of the gear under test to limit the horizontal position of the gear under test, a rotating shaft 6 to limit the rotation center of the gear under test, a retractable limiting block 11 connected to the rotating shaft to axially press the gear under test and transmit rotational torque to the gear under test, a shaft seat 7 to provide rotational support, and a motor 8 to provide rotational torque to the rotating shaft.

[0027] Specifically, the purging assembly includes an air outlet 2 and an air pump (not shown in the figure).

[0028] As will be understood by those skilled in the art, the operating principle and process of the purging assembly are conventional technical means well known to them, and therefore the operating principle and process of the purging assembly will not be described in detail here.

[0029] Specifically, based on the target rotational speed of 1000 rpm for performance testing of the gear under test, the time interval during which the gear under test reaches the target rotational speed from a stationary state is considered the acceleration phase of the gear under test, and the angular acceleration of the gear under test during the acceleration phase is 800 ± 50 rad / min. The acceleration time during the accelerated rotation phase is 400ms.

[0030] Specifically, the control module is a PLC controller.

[0031] As will be understood by those skilled in the art, the operating principle and process of a PLC controller are conventional technical means familiar to them, and therefore will not be elaborated upon here.

[0032] Specifically, the eddy current probe has an AC current of 2A flowing through its coil, an excitation frequency of 200kHz, and a diameter of 18.5mm.

[0033] Specifically, the coil is wound with copper Litz wire, and the coil material density is 8.92±0.05g / L. .

[0034] Specifically, the magnetic core is made of an iron-silicon-aluminum alloy, and its material density is 7.65 ± 0.03 g / L. .

[0035] Specifically, the fixing part is made of modified bisphenol A type epoxy resin, filled with 30wt% hollow glass microspheres, and the material density of the epoxy resin is 1.35±0.02g / L. .

[0036] As will be understood by those skilled in the art, the operating principle and process of eddy current probes are conventional technical means well known to them, and therefore the operating principle and process of eddy current probes will not be described in detail here.

[0037] Specifically, the induced electrical signals on the surface of the gear under test include, but are not limited to, induced voltage, impedance change, and phase difference.

[0038] As will be understood by those skilled in the art, detecting surface defects of the gear under test by collecting and analyzing induced electrical signals on the surface of the gear under test is a conventional technique well-known in the field of eddy current nondestructive testing. Therefore, the specific algorithms and processes for mapping and determining the impedance change characteristics or voltage fluctuation characteristics corresponding to the induced electrical signals as the distribution of cracks, pores or defects on the surface of the gear under test will not be elaborated here.

[0039] Specifically, the internal enclosure of the eddy current probe includes a coil 12 for generating an alternating magnetic field through alternating current, a magnetic core 13 for defining the area of ​​action of the alternating magnetic field, and a fixing part filled between the coil 12, the magnetic core 13 and the outer shell 17 of the eddy current probe for insulation, fixing and protection.

[0040] Specifically, the detection module includes: Vibration sensor 10, which is connected to the bracket, is used to acquire the vibration value of the eddy current probe; A dust concentration sensor array, which is horizontally arranged at equal intervals around the eddy current probe, is used to obtain the dust concentration at the dust concentration sampling point 9 below the eddy current probe.

[0041] Specifically, each dust concentration sampling point includes an infrared LED light source and a receiver with a wavelength of 850nm.

[0042] In one specific embodiment, the dust concentration sensor array has four dust concentration sampling points, and the straight-line distance between the horizontal plane of the ring formed by the four dust concentration sampling points and the upper surface of the gear to be tested is 3.2 mm.

[0043] As will be understood by those skilled in the art, the operating principles and processes of infrared LED light sources and receivers are conventional technical means well known to them, and therefore will not be elaborated upon here.

[0044] Specifically, the dust-containing area is the largest area enclosed by all dust concentration sampling points on the surface of the gear under test whose dust concentration is greater than a preset concentration. The corresponding fixed part area is the three-dimensional area occupied by the annular gap space formed between the single-turn coil and the surface of the magnetic core in the fixed part inside the housing of the eddy current probe.

[0045] Optionally, the test environment is set at a temperature of 25℃, a relative humidity of 50%, and a background dust concentration of 0.15±0.03mg / L. Under these conditions, the selectable range of the preset concentration is [0.80 mg / ]. 2.50mg / ].

[0046] Preferably, the preferred embodiment with a preset concentration is 1.20 mg / L. .

[0047] Please see Figure 4 As shown, this is a logic block diagram of the gear performance testing system based on mixed metal powder pressing according to an embodiment of the present invention, which determines the current rise slope of the alternating current. The control module is used to determine, based on the comparison result that the vibration difference of the gear under test during the accelerated rotation stage is greater than a preset difference, the wear degree of the contact interface of each component inside the eddy current probe does not meet the requirements, and reduces the current rise slope of the alternating current. The current rise slope of the alternating current is negatively correlated with the vibration difference. The vibration difference is the difference between the vibration value at the eddy current probe and the preset vibration reference value of the gear under test during the accelerated rotation phase.

[0048] Specifically, the vibration value is the effective value of the instantaneous acceleration at the eddy current probe collected by the vibration sensor during the accelerated rotation phase.

[0049] Specifically, if the vibration difference of the gear under test during the accelerated rotation phase is less than or equal to the preset difference, then the wear degree of the contact interface of each component inside the eddy current probe is determined to meet the requirements.

[0050] Specifically, when the target rotational speed for performance testing of the gear under test is 1000 rpm, the time interval during which the gear under test reaches the target rotational speed from a stationary state is considered the acceleration phase of the gear under test, and the angular acceleration of the gear under test during the acceleration phase is 800 ± 50 rad / min. Under these conditions, the preset vibration reference value is 0.25m / .

[0051] Optionally, the coil material density is 8.92±0.05 g / L. The density of the magnetic core material is 7.65 ± 0.03 g / L. The density of epoxy resin is 1.35 ± 0.02 g / L. The angular acceleration of the gear under test during the accelerated rotation phase is 800±50 rad / Given that the inertial force of the coil is 1.82±0.05N, the inertial force of the magnetic core is 1.56±0.04N, and the inertial force of the epoxy resin is 0.27±0.01N, the selectable range of the preset difference is [0.25m / 0.50m / ].

[0052] Preferably, the preferred embodiment with a preset difference amount is 0.35m / .

[0053] Those skilled in the art will understand that the selectable range of the preset difference amount, the preferred embodiment, and the value of the preset vibration reference value provided in this embodiment are based on the angular acceleration of the gear under test during the accelerated rotation phase being 800±50 rad / The values ​​selected under the conditions that the inertial force of the coil is 1.82±0.05N, the inertial force of the magnetic core is 1.56±0.04N, and the inertial force of the epoxy resin is 0.27±0.01N are the values ​​that best achieve the technical problem solved by the technical solution of the present invention. In actual applications or experiments, those skilled in the art can make adaptive adjustments to the preset difference amount according to the actual application environment and application scenario.

[0054] In implementation, when the vibration difference exceeds the preset difference value by 0.02m / When the current rise slope of the AC current is within a certain range, adjust it to 95% of the current rise slope of the current AC current. When the vibration difference exceeds the preset difference value by more than 0.02m / For every 0.01m / This reduces the current rise slope of the alternating current by 0.05 A / ms. In one specific embodiment, the current vibration difference is 0.40 m / s. The current rise slope of the current is currently 0.5 A / ms, and the current rise slope of the reduced current is 0.5 A / ms × 95% - (0.03 m / s). / 0.01m / ) × 0.05A / ms = 0.325A / ms.

[0055] Specifically, the current rise slope of the AC current is adjusted by a digital slope controller set in the control circuit of the alternating power supply.

[0056] In implementation, this invention reduces the current rise slope of the alternating current by setting the difference between the vibration value at the eddy current probe during the accelerated rotation of the gear under test and a preset vibration reference value. This reduces the instantaneous dielectric stress in the thinned insulation layer area under the action of high-frequency alternating current, thereby reducing the risk and scope of insulation layer breakdown. This overcomes the problem of vibrations generated during gear acceleration being transmitted to the eddy current probe, causing fretting wear between components inside the eddy current probe, which thins the insulation layer of the coil winding below the contact interface. This significantly increases the risk of insulation layer breakdown during subsequent high-frequency alternating current eddy current testing, thus reducing the risk of breakdown of some internal charge components. Dust escapes to the thinned outer surface of the insulation layer, making it easier for the charge on this surface to attract airborne dust. This reduces the actual distance between the thinned insulation layer and the eddy current probe, leading to detection errors. Specifically, during gear acceleration, the vibration generated is transmitted to the eddy current probe via the testing platform and support. When the excitation frequency of the vibration transmitted by the support approaches the natural frequency of the components encapsulated inside the eddy current probe during acceleration, it triggers a resonant response in the internal components. Due to the different material densities of the various components inside the eddy current probe—namely, the coil, magnetic core, and fixing parts—resonance occurs during vibration. The different inertial forces generated by the components amplify the relative displacement between them due to resonance, causing shear stress and fretting wear at the contact interfaces. This fretting wear thins the insulation layer of the coil windings below the contact interface. Subsequent eddy current testing with applied high-frequency alternating current accelerates the electro-aging of this thinned insulation layer. Under the same current, the electric field strength inside and on the surface of the electro-aged insulation layer increases. When the electric field strength approaches the dielectric breakdown threshold of the insulation layer, local polarization occurs on the surface. This local polarization causes the bound charges within the insulation material to gain sufficient energy, detach from their original atomic or molecular orbitals, and transform into free current carriers capable of migrating in the air. The charge then migrates towards the electrically aged insulation layer under the electric field of the alternating current, and is captured during the migration, unable to continue conducting. The captured charge accumulates at the interface, and the dust in the air attracted by the accumulated charge forms a non-conductive layer of uneven thickness between the probe and the surface of the gear under test. This results in the actual detection distance being smaller than the standard detection distance, causing a deviation in the measurement of the defect depth. Therefore, by reducing the current rise slope of the alternating current, the instantaneous dielectric stress in the thinned area of ​​the insulation layer under the electric field of the high-frequency alternating current is reduced, avoiding the accelerated local electrical aging of the insulation layer, weakening the attraction of the charge to the dust in the air, and further improving the accuracy of the gear performance testing system.

[0057] Specifically, the control module is used to determine, based on the judgment result that the overlap between the dust-existing area and the corresponding fixed part area is greater than the preset overlap, that the degree of influence of the environmental dust attracted by the leakage static electricity into the detection gap causes the surface defect detection of the gear under test to not meet the requirements, and to increase the vertical height of the bracket.

[0058] Optionally, under the conditions that the target speed for performance testing of the gear under test is 1000 rpm and the straight-line distance between the horizontal plane of the ring formed by each dust concentration sampling point and the upper surface of the gear under test is 3.2 mm, the preset overlap range is [40%, 65%].

[0059] Preferably, the preferred embodiment with a preset overlap ratio is 50%.

[0060] Those skilled in the art will understand that the range of preset overlap provided in this embodiment and the value of the preferred embodiment are the values ​​that best address the technical problem solved by the present invention, under the conditions that the target rotational speed for performance testing of the gear under test is 1000 rpm and the straight-line distance between the horizontal plane of the ring formed by the dust concentration sampling points and the upper surface of the gear under test is 3.2 mm. In actual applications or experiments, those skilled in the art can make adaptive adjustments to the preset overlap according to the actual application environment and application scenario.

[0061] Please see Figure 5 As shown, this is a structural schematic diagram of the corresponding fixed part region of the gear performance testing system based on mixed metal powder pressing in the dust presence area according to an embodiment of the present invention. The vertical height of the bracket is positively correlated with the overlap ratio. The overlap is the ratio of the projected area of ​​the corresponding fixed part region 15 on the dust existence region 16 to the area of ​​the dust existence region. The vertical height of the bracket is the shortest vertical distance between the bracket and the gear to be tested.

[0062] Specifically, the projection of the corresponding fixed part region 15 onto the dust-containing region 16 is the orthogonal projection of the corresponding fixed part region 15 downward along the vertical direction onto the plane where the surface 14 of the gear to be tested is located.

[0063] In implementation, when the overlap is greater than the preset overlap by less than 5%, the vertical height of the bracket is adjusted to 1.1 times the current vertical height of the bracket. When the overlap exceeds the preset overlap by more than 5%, the vertical height of the bracket is increased by 0.1mm for every 1% increase. In a specific embodiment, the current overlap is 57%, the current vertical height of the bracket is 2mm, and the increased vertical height of the bracket is 2mm × 1.1 + (2% / 1%) × 0.1mm = 2.4mm.

[0064] Specifically, the vertical height of the bracket is adjusted by a lifting module consisting of a servo motor, a ball screw, and a linear guide.

[0065] As will be understood by those skilled in the art, the operating principle and process of the lifting module composed of a servo motor, ball screw, and linear guide are conventional technical means well known to those skilled in the art. Therefore, the operating principle and process of the lifting module composed of a servo motor, ball screw, and linear guide will not be described in detail here.

[0066] In implementation, this invention increases the vertical height of the support by increasing the overlap between the dust-containing area and the corresponding fixed area of ​​the gear under test during uniform rotation, thereby reducing dust below the eddy current probe. This avoids signal shielding and eddy current path distortion caused by conductive dust, restores the effective penetration capability of the alternating magnetic field on the surface of the gear under test, and ensures the signal-to-noise ratio and spatial resolution of the surface defect acquisition of the gear under test. This overcomes the problem that dust below the eddy current probe, after being polarized in the electric field, is more easily attracted by electrostatic force and accumulates under the thinned insulation layer due to wear. Furthermore, the dust entering the gear under test... After the uniform rotation stage, the rotational speed of the gear under test tends to stabilize, and the inertial disturbance of dust particles is weakened. At this time, electrostatic adsorption force and gravitational settling become the dominant forces. The dust migrates along the electric field gradient direction and accumulates in the projection area directly below the fixed part between the coil and the magnetic core, that is, the projection area directly below the corresponding fixed part area. The higher the overlap, the stronger the spatial coupling between the electrostatic adsorption field source and the detection area of ​​the alternating magnetic field below the eddy current probe. This also increases the degree of interference of the eddy current signal by dust shielding and path distortion, further improving the accuracy of the gear performance testing system.

[0067] Specifically, the control module is used to determine, based on the judgment result that the decrease in dust concentration in the dust-existing area within a unit dust monitoring cycle is greater than a preset decrease, that the dust adsorbed by the trapped charge on the surface of the gear under test does not meet the requirements for the degree of contamination of the eddy current probe surface, and to extend the purging time of the purging assembly.

[0068] Optionally, the dust concentration in the current dust-scarce area is 2.20 mg / L. Given that the AC current of the eddy current probe is 2A and the linear distance between the gear under test and the eddy current probe is 3.3mm, the preset reduction range is [0.20mg / 0.40mg / ].

[0069] Preferably, the preferred embodiment with a predetermined reduced dosage is 0.25 mg / .

[0070] Those skilled in the art will understand that the selectable range of the preset reduction amount provided in this embodiment and the value of the preferred embodiment are based on a dust concentration of 2.20 mg / L in the current dust presence area. The optimal value selected under the conditions of 2A AC current of the eddy current probe and 3.3mm linear distance between the gear under test and the eddy current probe is the one that best addresses the technical problem solved by the present invention. In actual applications or experiments, those skilled in the art can make adaptive adjustments to the preset reduction amount according to the actual application environment and application scenario.

[0071] Specifically, the reduction in dust concentration is the difference between the dust concentration at the beginning and the end of a unit dust monitoring cycle in the area where the dust exists.

[0072] Specifically, the dust monitoring cycle per unit is 60ms.

[0073] Specifically, the purging time is positively correlated with the amount of reduction in dust concentration.

[0074] Specifically, the purging assembly is activated the moment the gear under test stops rotating.

[0075] During implementation, when the reduction in dust concentration exceeds the preset reduction value by 0.05 mg / L... If the dust concentration decreases by more than 0.05 mg / L, adjust the purging time to 1.1 times the current purging time. For every 0.01mg / This extends the purging time by 0.2 seconds. In one specific embodiment, the current dust concentration is reduced by 0.32 mg / L. The current purge duration is 3 seconds. The extended purge duration is 3 seconds × 1.1 + (0.2 mg / L). / 0.1mg / ) × 0.2s = 3.7s.

[0076] In implementation, this invention extends the purging time of the purging assembly based on the judgment that the decrease in dust concentration in the dust-existing area within a unit dust monitoring cycle is greater than a preset decrease. This utilizes airflow pressure to overcome the electrostatic adsorption force between dust particles and the probe surface, allowing the attached dust to gain sufficient kinetic energy to detach from the surface and be discharged with the airflow. This physically removes the dust contamination layer, restores the initial detection gap between the eddy current probe and the gear under test, and ensures the stability of alternating magnetic field energy transmission. It also overcomes the tendency of the electrostatic attraction of the insulation layer due to localized electro-aging to reach the surface of the eddy current probe. The electric field on the surface of the eddy current probe polarizes the dust, enhancing the attraction between the dust and the eddy current probe. At this point, electrostatic force becomes the dominant adsorption force for dust particles, and the electrostatic force's adsorption force on dust is far greater than... Due to the gravity of the dust itself, the captured dust particles are difficult to fall off by gravity or natural airflow, thus remaining on the surface of the eddy current probe. If dust is present on the surface of the eddy current probe, it will increase the background noise of the induced electrical signal received from the surface of the gear under test, which will lead to false sheet defects when detecting surface defects of the gear under test, resulting in a decrease in the accuracy of gear performance testing. The decrease in dust concentration in the dust-containing area within a unit dust monitoring cycle represents the amount of dust falling off the surface of the gear under test. When the decrease in dust concentration representing the amount of dust falling off is greater than the preset decrease, it indicates that the concentration in the dust-containing area is decreasing. The above measures improve the accuracy of performance testing of gears formed by pressing mixed metal powder.

[0077] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A gear performance testing system based on mixed metal powder pressing molding, characterized in that, include: The testing machine includes a rotating assembly for fixing and driving the gear to be tested, which is formed by pressing mixed metal powder, to rotate, and a bracket for limiting the testing height of the gear to be tested. The defect information acquisition module is connected to the testing machine and is used to acquire surface defect information of the gear under test. It includes an eddy current probe set above the gear under test to apply an alternating magnetic field to the gear under test to acquire the induced electrical signal generated when the gear under test interacts with the alternating magnetic field, and a purging assembly set on a bracket near the eddy current probe. The detection module is connected to the defect information acquisition module to obtain the vibration value of the eddy current probe and the dust concentration at the dust concentration sampling point below the eddy current probe. The control module, which is connected to the defect information acquisition module and the detection module respectively, is used to determine the current rise slope of the AC current based on the vibration difference of the gear under test during the accelerated rotation phase, determine the vertical height of the bracket based on the overlap between the dust presence area on the surface of the gear under test and the corresponding fixed part area during the uniform rotation phase, and determine the purging duration of the purging assembly based on the decrease in dust concentration in the dust presence area within a unit dust monitoring cycle.

2. The gear performance testing system based on mixed metal powder pressing as described in claim 1, characterized in that, The internal enclosure of the eddy current probe includes a coil for generating an alternating magnetic field through alternating current, a magnetic core for defining the area of ​​action of the alternating magnetic field, and a fixing part filled between the coil, the magnetic core, and the outer shell of the eddy current probe for insulation, fixing, and protection.

3. The gear performance testing system based on mixed metal powder pressing as described in claim 2, characterized in that, The detection module includes: A vibration sensor, connected to the bracket, is used to acquire the vibration value of the eddy current probe; A dust concentration sensor array, which is horizontally arranged at equal intervals around the eddy current probe, is used to obtain the dust concentration at the dust concentration sampling point below the eddy current probe.

4. The gear performance testing system based on mixed metal powder pressing as described in claim 3, characterized in that, The dust-containing area is the largest area enclosed by all dust concentration sampling points on the surface of the gear under test whose dust concentration is greater than a preset concentration. The corresponding fixed part area is the three-dimensional area occupied by the annular gap space formed between the single-turn coil and the surface of the magnetic core in the fixed part inside the housing of the eddy current probe.

5. The gear performance testing system based on mixed metal powder pressing as described in claim 4, characterized in that, The control module is used to determine, based on the comparison result that the vibration difference of the gear under test during the accelerated rotation phase is greater than a preset difference, whether the wear degree of the contact interface of each component internally encapsulated in the eddy current probe does not meet the requirements, and to reduce the current rise slope of the alternating current. The current rise slope of the alternating current is negatively correlated with the vibration difference. The vibration difference is the difference between the vibration value at the eddy current probe and the preset vibration reference value of the gear under test during the accelerated rotation phase.

6. The gear performance testing system based on mixed metal powder pressing as described in claim 5, characterized in that, The control module is used to determine, based on the judgment result that the overlap between the dust presence area and the corresponding fixed part area is greater than the preset overlap, the degree of influence of the environmental dust attracted by the leakage static electricity into the detection gap on the surface defect detection of the gear under test does not meet the requirements, and to increase the vertical height of the bracket.

7. The gear performance testing system based on mixed metal powder pressing as described in claim 6, characterized in that, The vertical height of the support is positively correlated with the degree of overlap, wherein, The overlap is the ratio of the projected area of ​​the corresponding fixed part region on the dust-existing area to the area of ​​the dust-existing area. The vertical height of the bracket is the shortest vertical distance between the bracket and the gear to be tested.

8. The gear performance testing system based on mixed metal powder pressing according to claim 7, characterized in that, The control module is used to determine, based on the judgment result that the decrease in dust concentration in the dust-existing area within a unit dust monitoring cycle is greater than a preset decrease, that the dust adsorbed by the trapped charge on the surface of the gear under test does not meet the requirements for the degree of contamination of the eddy current probe surface, and to extend the purging time of the purging assembly.

9. The gear performance testing system based on mixed metal powder pressing as described in claim 8, characterized in that, The reduction in dust concentration is the difference between the dust concentration at the beginning and the end of a unit dust monitoring cycle in the area where the dust exists.

10. The gear performance testing system based on mixed metal powder pressing according to claim 9, characterized in that, The purging time is positively correlated with the reduction in dust concentration.

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