A durability test device for a permanent magnet type stepping motor

Abstract

The application relates to the technical field of motor testing, in particular to a durability testing device for a permanent magnet type stepping motor, which comprises a testing machine, a driving piece, a piece to be tested, an electrical sensor and a grounding wire, and is characterized in that the device further comprises an electrical measurement shielding shell, an electrical isolation signal transmission shaft, a fixing plate, a bidirectional cam, an electromagnetic isolation assembly, an electrical measurement signal transmission connecting assembly and an electromagnetic damping type current discharge assembly; the electrical measurement shielding shell is fixed in the interior of the testing machine; the device solves the problems of heat attenuation, electric corrosion and electromagnetic interference leading to distortion of testing results in the prior art durability testing of the permanent magnet type stepping motor in a cooperative mode of the electrical measurement shielding shell, the electrical isolation signal transmission shaft, the bidirectional cam, the electromagnetic isolation assembly, the electrical measurement signal transmission connecting assembly and the electromagnetic damping type current discharge assembly, and has the remarkable advantages of high precision, high reliability and long service life testing.

Description

Technical Field

[0001] This invention relates to the field of motor testing technology, specifically to a durability testing device for permanent magnet stepper motors. Background Technology

[0002] Permanent magnet stepper motors are widely used in low-speed, light-load scenarios requiring precise angle control, such as air conditioning ducts, smart locks, camera pan-tilt units, small valves, and instrument pointers. Conducting long-term reliability and lifespan characteristic testing, measurement, and quantitative evaluation of these motors under operating conditions is crucial for ensuring their application stability. Permanent magnet stepper motor durability testing equipment, belonging to electrical parameter measurement and performance testing devices, is used to monitor the motor's operating status and lifespan assessment under long-term cyclic operating conditions. Its core function lies in using electrical measurement sensors (i.e., electrical sensors) to collect test and measurement parameters such as torque, load force, etc., in real time. Combined with actual operating condition simulation, it performs online monitoring and data acquisition of performance changes and failure characteristics during motor operation, providing real and effective measurement data support for motor lifespan assessment and reliability verification.

[0003] In the durability testing of permanent magnet stepper motors, to accurately obtain lifespan and reliability measurement data at different operating speeds, it is necessary to conduct electrical measurement tests simulating the actual operating conditions of the motor. Traditional durability testing devices use magnetic powder brakes as the test load. The mechanical energy output by the stepper motor cannot be effectively recovered; instead, it is completely converted into heat energy through mutual friction and shearing between the magnetic powder particles. As the speed increases, the slip power for the same torque increases exponentially. The magnetic powder brake generates intense heat at high speeds, causing the resistance torque to fluctuate with increasing temperature (thermal decay). This results in inconsistent test conditions, directly affecting the stability and consistency of electrical measurement parameter acquisition, leading to distorted measurement data and failing to provide a reliable basis for motor lifespan assessment.

[0004] Existing technology uses a servo motor as an active test load to replace the traditional passive brake. It can simulate various complex torque curves and can feed electrical energy back to the power grid through energy feedback technology. This effectively solves the thermal decay problem of magnetic powder brakes, ensures the stability of electrical measurement test conditions, and improves the initial consistency of measurement data. However, during long-term durability testing of stepper motors, the high-frequency common-mode current generated by the stepper motor driver and servo driver flows to the test sensor through the motor bearing. This weak but continuous electro-erosion (EDM) causes "acid-etched" pitting inside the bearing. This phenomenon is an electrical effect rather than mechanical wear, which can lead to abnormal early failure of the tested motor. This manifests as increased operating noise, abnormally high rotational resistance, and significant deterioration in positioning accuracy and torque output. This causes the durability test results to deviate from the motor's true mechanical life, seriously affecting the authenticity of the test data. At the same time, high-frequency electromagnetic noise can couple into the measurement signal of the torque sensor, causing pseudo-random fluctuations and false anomalies in the torque curve acquired by the host computer. This fails to accurately reflect the mechanical performance degradation and life characteristics of the motor itself, ultimately leading to misjudgment of motor life, distortion of reliability measurement data, and invalidation of test conclusions. This seriously affects the accuracy of electrical measurements and the reliability of data in durability testing, and cannot provide effective support for motor life assessment and reliability verification.

[0005] To address this, a durability testing device for permanent magnet stepper motors is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a durability testing device for permanent magnet stepper motors. By using an electrical measurement shielding shell, an electrical isolation signal transmission shaft, a bidirectional cam, an electromagnetic isolation component, an electrical measurement signal transmission connection component, and an electromagnetic damping current discharge component in a coordinated manner, this invention solves the problems of thermal decay, electrical corrosion, and electromagnetic interference-induced test result distortion in the durability testing of permanent magnet stepper motors in the prior art. It has the significant advantages of high precision, high reliability, and long lifespan testing.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A durability testing device for a permanent magnet stepper motor includes a testing machine, a driver, a device under test (DUT), an electrical sensor, and a grounding wire. It also includes an electrical measurement shielding housing, an electrically isolated signal transmission shaft, a fixing plate, a bidirectional cam, an electromagnetic isolation assembly, an electrical measurement signal transmission connection assembly, and an electromagnetically damped current discharge assembly. The electrical measurement shielding housing is fixed inside the testing machine. The electrically isolated signal transmission shaft is rotatably disposed inside the electrical measurement shielding housing. The fixing plate is fixed to the right end of the electrically isolated signal transmission shaft and is fixedly connected to the shaft of the driver. The bidirectional cam is fixed to the middle portion of the electrically isolated signal transmission shaft. The electromagnetic isolation assembly is disposed inside the electrical measurement shielding housing and is connected to the electrically isolated signal transmission shaft. The electrical measurement signal transmission connection assembly is disposed at the left end of the electrically isolated signal transmission shaft. Furthermore, it is connected to the device under test. The electromagnetic damping current discharge assembly is located inside the electrical measurement shielding shell. The gap between the electromagnetic damping current discharge assembly and the bidirectional cam is filled with conductive grease to form a low-impedance path for dynamic discharge of charge. When the electrically isolated signal transmission shaft is driven by the drive component to rotate rapidly in the forward direction, it simultaneously drives the bidirectional cam and the electromagnetic isolation assembly to rotate synchronously. During the rotation of the bidirectional cam, the electromagnetic damping current discharge assembly is compressed by its crest. The electromagnetic damping current discharge assembly remains compressed under the action of centrifugal force and does not interfere with the rotation of the bidirectional cam. During the reverse test, the drive component temporarily stops working, and the electromagnetic damping current discharge assembly loses the action of centrifugal force, releases the compression, and resets and springs up to obstruct the rotation of the bidirectional cam, so that the bidirectional cam and the electrically isolated signal transmission shaft quickly stop rotating in the forward direction.

[0009] Preferably, the electromagnetic isolation assembly includes two sets of isolation mating grooves and two sets of isolation meshing teeth. The two sets of isolation mating grooves are symmetrically opened on the inner wall of the electrical measurement shielding shell, and the two sets of isolation meshing teeth are symmetrically fixed on the surface of the electrical isolation signal transmission shaft. The isolation meshing teeth are engaged with the isolation mating grooves, and a very small gap is maintained between the isolation meshing teeth and the isolation mating grooves and filled with conductive grease.

[0010] Preferably, the electrical measurement signal transmission connection assembly includes a fixed base, a retaining ring, a connecting shaft, a measurement signal connection slot, and a measurement signal adapter block. The fixed base is fixed to the left end of the electrically isolated signal transmission shaft and is located on the left side of the electrical measurement shielding shell. The retaining ring is disposed at the top of the fixed base. The left end of the connecting shaft is fixed to the rotating shaft end of the device under test, and its right end extends into the groove formed by the retaining ring and the fixed base. The measurement signal connection slots are symmetrically opened at the top of the fixed base. The measurement signal adapter blocks are symmetrically fixed at the bottom of the retaining ring, and the measurement signal adapter blocks are engaged with the measurement signal connection slots.

[0011] Preferably, a connecting guide groove is provided on the inner axial part of the fixed base, and a connecting guide block is fixed to the right end of the connecting shaft, and the connecting guide block is engaged with the connecting guide groove.

[0012] Preferably, the right side of the connecting shaft is provided with symmetrical positioning grooves at both the upper and lower ends, and the inner sides of the fixing seat and the retaining ring are both fixed with positioning pieces, which are engaged with the positioning grooves.

[0013] Preferably, the outer side of the measurement signal adapter block is provided with a locking hole, the inner side of the measurement signal connection groove is provided with a threaded hole, and the threaded hole extends to the outer side of the fixing seat. The outer side of the fixing seat is provided with a bolt that passes through the inside of the threaded hole and is screwed into the locking hole.

[0014] Preferably, the electromagnetic damping current discharge assembly includes an internal slot, a fixed post, a buffer telescopic rod, a telescopic spring, a roller, and a plunger. The internal slot is arranged in a circular array on the inner wall of the electrical measurement shielding shell and is located between two sets of isolation mating slots. The fixed post is fixed inside the internal slot. The buffer telescopic rod is disposed inside the fixed post and its top end extends out of the fixed post. The telescopic spring is sleeved on the surface of the buffer telescopic rod and the fixed post, and its bottom end is connected to the bottom end of the fixed post. The roller is fixed to the top of the fixed post, and the plunger is fixed to the end of the roller. The plunger is placed in the trough of the bidirectional cam.

[0015] Preferably, the outer periphery of the roller is provided with a micron-sized oil storage groove for adsorbing conductive grease, so as to form a continuous liquid metal bridge between the roller and the bidirectional cam.

[0016] Preferably, the crest height of the bidirectional cam corresponds to the maximum stroke of the plunger, so that in emergency stop conditions, the telescopic spring is compressed to its maximum energy storage state, and the generated reaction torque is greater than the rated torque of the drive component.

[0017] Preferably, the bidirectional cam is made of a beryllium copper alloy with high conductivity, and conductive collector rings are provided at both ends of its axial direction to guide the induced current on the rotating shaft into the electrical measurement shielding shell through conductive grease.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. In the durability test of a permanent magnet stepper motor, this invention establishes an equipotential connection between the electrical measurement shield and the grounding wire, guiding the induced current to the ground to prevent electro-corrosion. Furthermore, electromagnetic shielding is achieved through the combination of an electromagnetic isolation component and conductive grease, reducing high-frequency noise interference to the test sensor signal. Consequently, the bidirectional cam and the electromagnetic damping current discharge component achieve interference-free forward rotation and emergency stop in reverse rotation under centrifugal force. The electrical measurement signal transmission connection component ensures a stable connection of the test component, thereby avoiding thermal attenuation and signal distortion during the test and effectively ensuring the accuracy of electrical sensor parameter acquisition. This fully guarantees the accuracy and reliability of the durability test results for the permanent magnet stepper motor.

[0020] 2. By using the isolation meshing teeth and isolation mating groove of the electromagnetic isolation component to form a dynamic electromagnetic barrier, high-frequency electromagnetic noise is confined inside the electrical measurement shielding shell. Then, the induced current is discharged with low impedance through the tiny gaps filled with conductive grease. At this time, during the high rotation of the electrical isolation signal transmission shaft, although the relative movement between the isolation meshing teeth and the isolation mating groove will generate a small amount of friction, compared with the electromagnetic shielding effect, this friction will not directly affect the operational stability of the test device. Therefore, the torque signal collected by the electrical sensor is the true output characteristic of the motor, which can ensure the detection accuracy of the electrical sensor parameters and further guarantee the reliability and validity of the durability test data of the permanent magnet stepper motor.

[0021] 3. A dynamic braking structure is formed by the cooperation of a bidirectional cam, a fixed column, a buffer telescopic rod, a telescopic spring, a roller, and a plunger. The centrifugal force when the motor rotates forward is converted into the compressed energy stored in the telescopic spring. Then, low-friction transmission is achieved through the rolling contact between the roller and the bidirectional cam. At this time, during the reversing test drive, the telescopic spring releases its stored energy and pushes the plunger into the trough of the bidirectional cam. Although a momentary impact torque is generated, compared with the emergency stop response speed, this impact will not directly affect the braking accuracy of the test device. Then, the rapid reset of the electromagnetic damping current discharge component achieves millisecond-level stopping of the electrically isolated signal transmission shaft. This ensures the stability of the test conditions when switching between forward and reverse rotation, and further guarantees the accuracy and repeatability of the dynamic response characteristic test of the permanent magnet stepper motor. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 For the present invention Figure 1 Enlarged schematic diagram of the structure at point A in the diagram;

[0024] Figure 3 This is a cross-sectional view of the electrically isolated signal transmission shaft structure of the present invention;

[0025] Figure 4 This is a cross-sectional view of the bidirectional cam structure of the present invention;

[0026] Figure 5 This is an exploded view of the electrical measurement signal transmission connection component structure of the present invention;

[0027] Figure 6 This is an exploded view of the electrically isolated signal transmission shaft structure of the present invention;

[0028] Figure 7 This is a schematic diagram of the electrical measurement shielding shell structure of the present invention;

[0029] Figure 8 This is a schematic diagram of the electrically isolated signal transmission shaft structure of the present invention;

[0030] Figure 9 This is an exploded view of the electromagnetic damping current discharge assembly structure of the present invention.

[0031] In the diagram: 1. Testing machine; 2. Driving component; 3. Test piece; 4. Electrical sensor; 5. Electrical measurement shielding housing; 51. Grounding wire; 6. Electrically isolated signal transmission shaft; 61. Fixing plate; 7. Bidirectional cam; 8. Electromagnetic isolation assembly; 81. Isolation mating groove; 82. Isolation meshing teeth; 9. Electrical measurement signal transmission connection assembly; 91. Fixing base; 911. Connecting guide groove; 912. Positioning piece; 92. Snap ring; 93. Connecting shaft; 931. Connecting guide block; 932. Positioning groove; 94. Measurement signal connection groove; 941. Screw hole; 95. Measurement signal adapter block; 951. Locking hole; 96. Bolt; 10. Electromagnetic damping current discharge assembly; 101. Internal groove; 102. Fixing column; 103. Buffer telescopic rod; 104. Telescopic spring; 105. Roller; 106. Plunger. Detailed Implementation

[0032] 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.

[0033] Please see Figures 1 to 9 This invention provides a durability testing device for permanent magnet stepper motors, the technical solution of which is as follows:

[0034] Reference Figure 1 , Figure 2 and Figure 3A durability testing device for permanent magnet stepper motors includes a testing machine 1, a driving component 2, a device under test (DUT) 3, an electrical sensor 4, and a grounding wire 51. The driving component 2 and the DUT 3 are both fixed inside the testing machine 1 and are positioned opposite each other. The electrical sensor 4 is located on one side of the DUT 3, and it collects key electrical sensor parameters such as torque, load force, etc., in real time and transmits them to a host computer. The grounding wire 51 is a flexible flat strip braided from multiple strands of copper wire, and its surface is covered with a high-temperature resistant insulating layer. The grounding wire 51 is connected to the front end of an electrical measurement shielding shell 5, and it penetrates the bottom end of the testing machine 1 to form an equipotential connection with the ground at a reference potential. The grounding wire 51 connects the electrical measurement shielding shell 5 to the ground, conducts induced current, and prevents electrical corrosion. To prevent damage to the bearing of the test component 3 (EDM) and ensure electrical safety of the equipment, the grounding wire 51, as a key conduction path for electrical safety and electromagnetic protection, is a flexible flat strip woven from multi-strand copper wires. It possesses high conductivity and flexibility, adapting to the complex wiring requirements inside the testing machine 1 and preventing breakage due to vibration or installation stress. The high-temperature resistant insulation layer covering its surface isolates it from external environmental interference (such as humidity and dust) and prevents electric shock risks to operators. It is particularly suitable for the high-temperature environment generated by the long-term operation of the test component 3 and the drive component 2 during durability testing. The induced current captured by the electrical measurement shielding shell 5 (such as stray current generated by electromagnetic radiation from the shaft end of the drive component 2) is conducted to the ground through the grounding path, preventing current from forming electrolytic corrosion through the bearing of the test component 3. EDM (Electrical Discharge Management) ensures the authenticity and accuracy of the test of the device under test (DUT) 3. It also includes an electrical measurement shielding housing 5, an electrically isolated signal transmission shaft 6, a fixing plate 61, a bidirectional cam 7, an electromagnetic isolation assembly 8, an electrical measurement signal transmission connection assembly 9, and an electromagnetic damping current discharge assembly 10. The electrical measurement shielding housing 5 is fixed inside the testing machine 1, enclosing the core components and blocking external electromagnetic interference. As part of the electromagnetic isolation assembly 8, it prevents high-frequency electromagnetic noise from coupling to the sensor signal, ensuring the accuracy of the test data. The electrically isolated signal transmission shaft 6 is rotatably mounted inside the electrical measurement shielding housing 5. The electrically isolated signal transmission shaft 6 transmits power from the driving component 2 to the DUT 3 and simultaneously drives the bidirectional cam 7 and the electromagnetic isolation assembly 8. The rotation of component 8 enables power transmission and coordinated action of multiple components, ensuring stable test conditions. The fixing plate 61 is fixed to the right end of the electrically isolated signal transmission shaft 6 and is fixedly connected to the rotating shaft of the drive component 2. The fixing plate 61 is used to fix the rotating shaft of the drive component 2 and the electrically isolated signal transmission shaft 6, ensuring no slippage in power transmission, improving transmission efficiency, and avoiding test errors caused by loose connections. The bidirectional cam 7 is fixed in the middle of the electrically isolated signal transmission shaft 6. The bidirectional cam 7 cooperates with the electromagnetic damping current discharge assembly 10 through its crest, achieving interference-free forward rotation and emergency stop before reverse rotation. During forward rotation, it compresses the electromagnetic damping current discharge assembly 10; before reverse rotation, it uses its restoring force for rapid braking, shortening the commutation time. The electromagnetic isolation assembly 8 is located inside the electrical measurement shielding housing 5.Furthermore, it is connected to the electrically isolated signal transmission shaft 6. The electromagnetic isolation component 8 and the electrical measurement shielding shell 5 form an electromagnetic shielding space, and the gap is filled with conductive grease to further isolate electromagnetic radiation and prevent the spread of interference signals. The electrical measurement signal transmission connection component 9 is located at the left end of the electrically isolated signal transmission shaft 6 and is connected to the test piece 3. The electrical measurement signal transmission connection component 9 mechanically connects the test piece 3 and the electrically isolated signal transmission shaft 6 to ensure coaxiality and transmission stability, realize quick assembly and disassembly and precise positioning, and reduce test preparation time. The electromagnetic damping current discharge component 10 is located inside the electrical measurement shielding shell 5. The gap between the electromagnetic damping current discharge component 10 and the bidirectional cam 7 is filled with conductive grease. The electromagnetic damping current discharge component 10 cooperates with the bidirectional cam 7 through the telescopic spring 104 and the plunger 106 to achieve dynamic braking. When rotating forward, it is compressed by centrifugal force, and before rotating backward, it releases stored energy to hinder the rotation of the cam. This design achieves rapid emergency stop, preventing the motor's inertia from affecting test results. Conductive grease fills the gap between the electromagnetic damping current discharge assembly 10 and the bidirectional cam 7, reducing frictional resistance during relative motion, minimizing mechanical wear, and providing a seal to prevent dust and other impurities from affecting normal operation. When the electrically isolated signal transmission shaft 6 is driven by the drive component 2 to rotate rapidly forward, it simultaneously drives the bidirectional cam 7 and the electromagnetic isolation assembly 8 to rotate synchronously. During rotation, the bidirectional cam 7 compresses the electromagnetic damping current discharge assembly 10 through its crest. The electromagnetic damping current discharge assembly 10 remains compressed under centrifugal force, preventing interference with the rotation of the bidirectional cam 7. During reverse rotation testing, the drive component 2 temporarily stops, and the electromagnetic damping current discharge assembly 10 loses the centrifugal force, releasing its compression and resetting to prevent the bidirectional cam 7 from rotating, thus quickly stopping the forward rotation of both the bidirectional cam 7 and the electrically isolated signal transmission shaft 6.

[0035] Reference Figure 3 , Figure 6 , Figure 7 and Figure 8In one embodiment of the present invention, the electromagnetic isolation assembly 8 specifically includes two sets of isolation mating grooves 81 and two sets of isolation meshing teeth 82. The two sets of isolation mating grooves 81 are symmetrically formed on the inner wall of the electrical measurement shielding shell 5. The two sets of isolation mating grooves 81 provide a rotation track for the isolation meshing teeth 82, ensuring that the electrically isolated signal transmission shaft 6 maintains coaxiality during rotation. Simultaneously, as a fixed part of the electromagnetic shielding, they form the boundary of the "cage" of the Faraday cage. The two sets of isolation meshing teeth 82 are symmetrically fixed on the surface of the electrically isolated signal transmission shaft 6, rotating synchronously with the electrically isolated signal transmission shaft 6, forming a dynamic seal with the isolation mating grooves 81. The electromagnetic shielding gap, in conjunction with conductive grease, enables the "capture" and conduction of electromagnetic radiation from the shaft end. The isolation meshing teeth 82 and the isolation mating groove 81 engage and connect, maintaining a very small gap between the isolation meshing teeth 82 and the isolation mating groove 81 and filling it with conductive grease. Utilizing conductivity, the induced current on the electrically isolated signal transmission shaft 6 is conducted through the isolation meshing teeth 82 → conductive grease → isolation mating groove 81 to the electrical measurement shielding shell 5, and finally discharged through the grounding wire 51, avoiding electro-corrosion. At the same time, it reduces mechanical friction between the isolation meshing teeth 82 and the isolation mating groove 81, preventing dust, moisture and other impurities from entering the gap and affecting the shielding effect.

[0036] Reference Figure 2 and Figure 5In one embodiment of the present invention, the electrical measurement signal transmission connection assembly 9 specifically includes a fixed base 91, a retaining ring 92, a connecting shaft 93, a measurement signal connection groove 94, and a measurement signal adapter block 95. The fixed base 91 is fixed to the left end of the electrically isolated signal transmission shaft 6 and is located on the left side of the electrical measurement shielding shell 5. As the basic carrier of the electrical measurement signal transmission connection assembly 9, it cooperates with the retaining ring 92 to form a groove for accommodating the connecting shaft 93, so as to constrain the radial and axial displacement of the connecting shaft 93 through mechanical structure, ensure transmission coaxiality, and avoid torque fluctuations caused by loose connection during testing. The retaining ring 92 is set at the top of the fixed base 91. The axial locking of the connecting shaft 93 is achieved by the engagement of the measurement signal adapter block 95 and the measurement signal connection groove 94, so as to clamp the connecting shaft 93 together with the fixed base 91, preventing it from falling off during rotation, and facilitating the disassembly and installation of the test piece 3. The left end of the connecting shaft 93 is fixed to the rotating shaft end of the test piece 3, and its right end... Extending into the groove formed by the combination of the retaining ring 92 and the fixed base 91, its left end is fixed to the end of the shaft of the test piece 3, and its right end is embedded in the combined groove of the fixed base 91 and the retaining ring 92. It serves as a rigid transmission medium between the test piece 3 and the electrically isolated signal transmission shaft 6, ensuring lossless power transmission. At the same time, through structural design, it can adapt to the shaft interface of different models of test pieces 3. The measurement signal connection groove 94 is symmetrically opened at the top of the fixed base 91 to accommodate the measurement signal adapter block 95. The retaining ring 92 and the fixed base 91 are accurately positioned by engaging with the measurement signal adapter block 95, limiting the relative displacement between the two and ensuring connection stability. The measurement signal adapter block 95 is symmetrically fixed at the bottom of the retaining ring 92. The measurement signal adapter block 95 engages with the measurement signal connection groove 94, forming a concave-convex fit structure with the measurement signal connection groove 94. It serves as a mechanical interlocking component between the retaining ring 92 and the fixed base 91. It can be quickly assembled by embedding into the measurement signal connection groove 94, and at the same time, it can withstand the radial force during the transmission process.

[0037] Reference Figure 3 and Figure 5 In one embodiment of the present invention, a connecting guide groove 911 is provided on the inner axial part of the fixed base 91, which cooperates with the connecting guide block 931 of the connecting shaft 93. The connecting shaft 93 and the fixed base 91 are precisely aligned through the interlocking of the concave and convex parts, so as to avoid transmission jamming or stress concentration caused by eccentricity during installation and ensure the coaxiality of power transmission. The right end of the connecting shaft 93 is fixed with the connecting guide block 931, which is engaged with the connecting guide groove 911. It serves as the positioning reference of the connecting shaft 93, ensuring the axial position accuracy when it is inserted into the fixed base 91 and reducing the impact of assembly errors on test data. The connecting guide block 931 is engaged with the connecting guide groove 911.

[0038] Reference Figure 3 and Figure 5As one embodiment of the present invention, specifically, positioning grooves 932 are symmetrically provided at the upper and lower ends of the right side of the connecting shaft 93 to accommodate positioning pieces 912. By engaging with the positioning pieces 912, the circumferential rotation of the connecting shaft 93 is restricted, preventing relative slippage caused by torque during transmission and ensuring torque transmission efficiency. Positioning pieces 912 are fixed on the inner sides of the fixed seat 91 and the retaining ring 92, which can engage with the positioning grooves 932 to further lock the connecting shaft 93 in the radial direction. Together with the connecting guide block 931 and the connecting guide groove 911, a "axial + circumferential" dual positioning is formed to improve connection stability. The positioning pieces 912 are engaged with the positioning grooves 932.

[0039] Reference Figure 5 As one embodiment of the present invention, specifically, a locking hole 951 is provided on the outer side of the measurement signal adapter block 95, which can be used with the bolt 96 to achieve mechanical locking. A screw hole 941 is provided through the inner side of the measurement signal connection groove 94, which serves as the installation channel for the bolt 96. The screw hole 941 extends to the outer side of the fixing seat 91. The outer side of the fixing seat 91 is provided with a bolt 96 that passes through the inside of the screw hole 941 and is screwed into the locking hole 951. This can rigidly lock the retaining ring 92 to the fixing seat 91, forming a closed clamping space and ensuring the structural stability of the connecting shaft 93 when it rotates at high speed.

[0040] Reference Figure 3 , Figure 4 , Figure 6 and Figure 9As one embodiment of the present invention, specifically, the electromagnetic damping current discharge assembly 10 includes an internal groove 101, a fixed post 102, a buffer telescopic rod 103, a telescopic spring 104, a roller 105, and a plunger 106. The internal groove 101 is circularly arrayed on the inner wall of the electrical measurement shielding shell 5 and is located between two sets of isolation mating grooves 81. It is used to accommodate the core components of the electromagnetic damping current discharge assembly 10 and provide installation and positioning space for the fixed post 102. The fixed post 102 is fixed inside the internal groove 101 and serves as a support carrier for the buffer telescopic rod 103 and the telescopic spring 104. It restricts the radial displacement of the buffer telescopic rod 103 and ensures its stable axial extension and contraction, avoiding skewing under centrifugal force. The buffer telescopic rod 103 is disposed inside the fixed post 102, and its top end extends out of the interior of the fixed post 102. It transmits the elastic force of the telescopic spring 104 through axial extension and contraction, driving the roller 106. 5. Contact or separation with the bidirectional cam 7 realizes the switching of braking state. The telescopic spring 104 is sleeved on the surface of the buffer telescopic rod 103 and the fixed column 102, and its bottom end is connected to the bottom end of the fixed column 102. When rotating forward, it is compressed and stored by the crest of the bidirectional cam 7. Before rotating in reverse, it releases potential energy to push the buffer telescopic rod 103 to reset, generating a braking reaction torque. This torque is greater than the rated torque of the drive component 2, ensuring the emergency stop effect. The roller 105 is fixed at the top of the fixed column 102, which changes the rotational friction of the bidirectional cam 7 from sliding friction to rolling friction, reducing mechanical wear and improving service life. The plunger 106 is fixed at the end of the roller 105. The plunger 106 is placed in the trough of the bidirectional cam 7. As the direct component in contact with the bidirectional cam 7, the plunger 106 achieves physical resistance to the rotation of the bidirectional cam 7 by embedding in the trough. The crest height corresponds to the stroke of the plunger 106, ensuring that the telescopic spring 104 is compressed to the maximum energy storage state when the emergency stop is performed.

[0041] Reference Figure 3 and Figure 4In one embodiment of the present invention, the outer periphery of the roller 105 is provided with a micron-sized oil reservoir for adsorbing conductive grease, thereby forming a continuous liquid metal bridge between the roller 105 and the bidirectional cam 7. Through the microstructure of the micron-sized oil reservoir, conductive grease is actively adsorbed and retained, ensuring that a conductive medium is continuously present at the contact interface between the roller 105 and the bidirectional cam 7. When the roller 105 and the bidirectional cam 7 move relative to each other, the conductive grease adsorbed in the oil reservoir can maintain the conductive path between them, avoiding grease loss or local drying caused by mechanical friction, and ensuring the stability of induced current conduction. As a low-impedance conductive channel, the liquid metal bridge can efficiently transmit the induced current on the bidirectional cam 7 to the roller 105, and then guide it into the electrical measurement shielding shell 5 through the electromagnetic damping current discharge component 10, and finally release it through the grounding wire 51, effectively suppressing the risk of electro-corrosion. Moreover, the conductive grease forms a lubricating layer at the contact interface, reducing the coefficient of friction between the roller 105 and the bidirectional cam 7, reducing mechanical wear, and extending the service life of the component.

[0042] Reference Figure 3 , Figure 4 and Figure 8 As one embodiment of the present invention, specifically, the peak height of the bidirectional cam 7 corresponds to the maximum stroke of the plunger 106, so that in the emergency stop condition, the telescopic spring 104 is compressed to the maximum energy storage state, providing sufficient reaction torque for braking, and the generated reaction torque is greater than the rated torque of the drive component 2, realizing the rapid braking of the electrically isolated signal transmission shaft 6, and ensuring the response speed and test accuracy when switching between forward and reverse rotation tests.

[0043] Reference Figure 4 and Figure 6 As one embodiment of the present invention, specifically, the bidirectional cam 7 is made of a beryllium copper alloy with high conductivity. Utilizing the excellent conductivity of beryllium copper alloy as the medium for conducting induced current, it can quickly conduct the induced current (such as stray current formed by electromagnetic radiation) generated when the electrically isolated signal transmission shaft 6 rotates to the axial collector ring, avoiding the risk of electro-corrosion caused by current accumulation. Furthermore, conductive collector rings are provided at both ends of its axial direction to guide the induced current on the rotating shaft into the electrical measurement shielding shell 5 through conductive grease. A conductive path is formed between the conductive grease and the electrical measurement shielding shell 5, and the induced current collected by the bidirectional cam 7 body is poured into the electrical measurement shielding shell 5 through the conductive grease, and finally released to the ground through the grounding wire 51, realizing a complete conductive path of "rotating shaft → bidirectional cam 7 → collector ring → conductive grease → electrical measurement shielding shell 5 → grounding wire 51".

[0044] Working Principle: During the durability test of a permanent magnet stepper motor, the test piece 3 is first installed on the test base. Then, the test piece 3 is securely connected to the electrically isolated signal transmission shaft 6 via the electrical measurement signal transmission connection assembly 9. Next, the drive unit 2 is started, and the shaft of the drive unit 2 drives the fixed plate 61 to rotate, thereby causing the electrically isolated signal transmission shaft 6 to rotate inside the electrical measurement shielding shell 5. As the electrically isolated signal transmission shaft 6 rotates, it simultaneously drives the bidirectional cam 7 and the electromagnetic isolation assembly 8 to rotate synchronously. During the rapid forward rotation of the electrically isolated signal transmission shaft 6, the bidirectional cam 7 rotates synchronously, and its peaks compress the electromagnetic damping current discharge assembly 10. At this time, the electromagnetic damping current discharge assembly 10 remains compressed under centrifugal force and does not interfere with the rotation of the bidirectional cam 7. The test piece 3 operates normally for the durability test. When the drive unit 2 stops outputting power and prepares for the reverse rotation test, the electromagnetic damping current discharge assembly 10 loses its centrifugal force. The electromagnetic damping current discharge assembly 10 and the bidirectional cam 7 interfere with the rotation of the bidirectional cam 7, thereby forcing the rotating shafts of the drive component 2 and the test component 3, as well as the electrically isolated signal transmission shaft 6, to stop within a very short stroke. When the drive component 2 provides a reverse current, the electromagnetic damping current discharge assembly 10 and the bidirectional cam 7 can help the motor overcome inertia, thus enabling rapid switching between forward and reverse rotation tests. Throughout the test, the electrical measurement shielding shell 5 acts as a shield against battery interference. The electromagnetic isolation assembly 8 ensures the normal rotation of the electrically isolated signal transmission shaft 6 and effectively prevents high-frequency battery noise from coupling into the analog signal of the sensor, avoiding pseudo-random fluctuations and false anomalies in the torque curve collected by the host computer. This ensures that the test structure can truly reflect the mechanical performance degradation and lifespan characteristics of the test component 3 itself. At the same time, the grounding wire 51 conducts the induced current on the electrical measurement shielding shell 5 to the ground, further ensuring the electrical safety of the test device and the accuracy of the test data.

[0045] Specifically, before performing a durability test on the test piece 3 using the drive unit 2, first loosen the bolts 96 on both sides of the fixing base 91, allowing them to be screwed into the screw hole 941 from inside the locking hole 951. Then, lift the retaining ring 92 upwards to separate the measurement signal adapter block 95 from the measurement signal connection groove 94. At this point, insert the connecting shaft 93 at the end of the drive unit 2 into the groove formed by the retaining ring 92 and the fixing base 91, ensuring that the connecting guide block 931 is accurately engaged in the connecting guide groove 911. Simultaneously, the positioning piece 912 on the fixing base 91 must also engage with the positioning groove 932 at the bottom of the connecting shaft 93. After completing the above steps, lower the retaining ring 92 back down, allowing the measurement signal adapter block 95 to re-embed into the measurement signal connection groove 94, and simultaneously allow the retaining ring 92 to... The positioning plate 912 on the upper part engages with the positioning groove 932 at the bottom of the connecting shaft 93. Then, the bolt 96 is tightened through the threaded hole 941 and the locking hole 951 to achieve a firm lock between the retaining ring 92 and the fixed seat 91, thereby ensuring a stable transmission connection between the test piece 3 and the electrically isolated signal transmission shaft 6. Then, the drive component 2 is started to rotate forward. The rotating shaft of the drive component 2 drives the fixed plate 61 to rotate, and the electrically isolated signal transmission shaft 6 rotates inside the electrical measurement shielding shell 5. During the rapid forward rotation of the electrically isolated signal transmission shaft 6, the bidirectional cam 7 rotates synchronously. Its rotation crest rolls and rubs against the plunger 106 and the roller 105. During the rolling friction, it will simultaneously push the buffer telescopic rod 103 into the interior of the fixed column 102 and compress the telescopic spring. 104, so that it is in an energy storage state. At this time, the electromagnetic damping current discharge assembly 10 maintains a relatively compressed and stable shape under the action of centrifugal force, and will not cause additional interference to the normal rotation of the bidirectional cam 7. The test piece 3 can run in the initial stage of the durability test under normal operating conditions. When the drive piece 2 stops outputting power according to the test procedure and prepares to reverse the direction for the reverse test, the rotation speed of the electrically isolated signal transmission shaft 6 drops rapidly, and the centrifugal force on the electromagnetic damping current discharge assembly 10 also decreases sharply. The telescopic spring 104 begins to release the elastic potential energy stored before, pushing the buffer telescopic rod 103 to extend outward, thereby causing the roller 105 and the plunger 106 to move outward. The plunger 106 generates an interaction force with the inner wall of the trough of the bidirectional cam 7. The bidirectional cam 7 effectively interferes with the rotation of the bidirectional cam 7. This interference force is transmitted to the rotating shaft of the drive component 2 through the electrically isolated signal transmission shaft 6 and the fixed plate 61, forcing the rotating shafts of the drive component 2 and the test component 3, as well as the electrically isolated signal transmission shaft 6, to stop within a very short stroke, achieving an emergency stop effect. When the drive component 2 provides a reverse current, the bidirectional cam 7 continues to rotate, and its crest contacts the plunger 106 and roller 105 again, causing the plunger 106, roller 105, and telescopic spring 104 to be compressed again under the action of the bidirectional cam 7. However, since the rotation direction of the bidirectional cam 7 has changed, and through the action of the electromagnetic damping current discharge component 10 and the bidirectional cam 7, it can help the drive component 2, the test component 3, and the electrically isolated signal transmission shaft 6 overcome inertia.This facilitates the reversal of the test piece 3, enabling rapid and smooth switching between forward and reverse testing. Simultaneously, the rotation of the electrically isolated signal transmission shaft 6 drives the isolation meshing teeth 82 to rotate within the isolation mating groove 81, maintaining a very small gap filled with conductive grease. This forms a dynamic Faraday cage, physically locking the electromagnetic radiation from the drive component 2's shaft end within the electrical measurement shielding shell 5, preventing it from diffusing into the induction coil of the test piece 3. This completely isolates the interference source physically, allowing the test to continue until the mechanical fatigue endpoint of the test piece 3 is reached.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A durability testing device for a permanent magnet stepper motor, comprising a testing machine, a driver, a device under test, an electrical sensor, and a grounding wire, characterized in that: The system also includes an electrical measurement shielding housing, an electrically isolated signal transmission shaft, a fixing plate, a bidirectional cam, an electromagnetic isolation assembly, an electrical measurement signal transmission connection assembly, and an electromagnetically damped current discharge assembly. The electrical measurement shielding housing is fixed inside the testing machine. The grounding wire is connected to the front end of the electrical measurement shielding housing and passes through the bottom of the testing machine to form an equipotential connection with the ground at a reference potential. The electrically isolated signal transmission shaft is rotatably mounted inside the electrical measurement shielding housing. The fixing plate is fixed to the right end of the electrically isolated signal transmission shaft and is fixedly connected to the rotating shaft of the driving component. The bidirectional cam is fixed to the middle part of the electrically isolated signal transmission shaft. The electromagnetic isolation assembly is located inside the electrical measurement shielding housing and is connected to the electrically isolated signal transmission shaft. The electrical measurement signal transmission connection assembly is located at the left end of the electrically isolated signal transmission shaft. The electromagnetic damping current discharge assembly is connected to the device under test. The electromagnetic damping current discharge assembly is located inside the electrical measurement shielding shell. The gap between the electromagnetic damping current discharge assembly and the bidirectional cam is filled with conductive grease to form a low-impedance path for dynamic discharge of charge. When the electrically isolated signal transmission shaft is driven by the drive component to rotate rapidly in the forward direction, it simultaneously drives the bidirectional cam and the electromagnetic isolation assembly to rotate synchronously. During the rotation of the bidirectional cam, the electromagnetic damping current discharge assembly is compressed by its crest. The electromagnetic damping current discharge assembly remains compressed under the action of centrifugal force and does not interfere with the rotation of the bidirectional cam. During the reverse test, the drive component temporarily stops working, and the electromagnetic damping current discharge assembly loses the action of centrifugal force, releases the compression, and resets and springs up to obstruct the rotation of the bidirectional cam, so that the bidirectional cam and the electrically isolated signal transmission shaft quickly stop rotating in the forward direction. The electromagnetic damping current discharge assembly includes an internal slot, a fixed post, a buffer telescopic rod, a telescopic spring, a roller, and a plunger. The internal slot is arranged in a circular array on the inner wall of the electrical measurement shielding shell and is located between two sets of isolation mating slots. The fixed post is fixed inside the internal slot. The buffer telescopic rod is disposed inside the fixed post and its top extends out of the fixed post. The telescopic spring is sleeved on the surface of the buffer telescopic rod and the fixed post, and its bottom end is connected to the bottom end of the fixed post. The roller is fixed at the top of the fixed post, and the plunger is fixed at the end of the roller. The plunger is placed in the trough of the bidirectional cam. The outer periphery of the roller is provided with a micron-sized oil storage groove for adsorbing conductive grease, so as to form a continuous liquid metal bridge between the roller and the bidirectional cam.

2. The durability testing device for a permanent magnet stepper motor according to claim 1, characterized in that: The electromagnetic isolation assembly includes two sets of isolation mating grooves and two sets of isolation meshing teeth. The two sets of isolation mating grooves are symmetrically opened on the inner wall of the electrical measurement shielding shell, and the two sets of isolation meshing teeth are symmetrically fixed on the surface of the electrical isolation signal transmission shaft. The isolation meshing teeth are engaged with the isolation mating grooves, and a very small gap is maintained between the isolation meshing teeth and the isolation mating grooves and filled with conductive grease.

3. The durability testing device for a permanent magnet stepper motor according to claim 1, characterized in that: The electrical measurement signal transmission connection assembly includes a fixed base, a retaining ring, a connecting shaft, a measurement signal connection slot, and a measurement signal adapter block. The fixed base is fixed to the left end of the electrically isolated signal transmission shaft and is located on the left side of the electrical measurement shielding shell. The retaining ring is disposed at the top of the fixed base. The left end of the connecting shaft is fixed to the shaft end of the device under test, and its right end extends into the groove formed by the retaining ring and the fixed base. The measurement signal connection slots are symmetrically opened at the top of the fixed base. The measurement signal adapter blocks are symmetrically fixed at the bottom end of the retaining ring, and the measurement signal adapter blocks are engaged with the measurement signal connection slots.

4. The durability testing device for a permanent magnet stepper motor according to claim 3, characterized in that: The inner axial part of the fixed base is provided with a connecting guide groove, and the right end of the connecting shaft is fixed with a connecting guide block, which is engaged with the connecting guide groove.

5. The durability testing device for a permanent magnet stepper motor according to claim 4, characterized in that: The connecting shaft has symmetrical positioning grooves at its upper and lower ends on the right side. The inner sides of the fixing seat and the retaining ring are both fixed with positioning pieces, which are engaged with the positioning grooves.

6. The durability testing device for a permanent magnet stepper motor according to claim 3, characterized in that: The outer side of the measurement signal adapter block is provided with a locking hole, and the inner side of the measurement signal connection groove is provided with a threaded hole that extends to the outer side of the fixing seat. The outer side of the fixing seat is provided with a bolt that passes through the inside of the threaded hole and is screwed into the locking hole.

7. The durability testing device for a permanent magnet stepper motor according to claim 1, characterized in that: The peak height of the bidirectional cam corresponds to the maximum stroke of the plunger, so that in emergency stop conditions, the telescopic spring is compressed to its maximum energy storage state, and the generated reaction torque is greater than the rated torque of the drive component.

8. The durability testing device for a permanent magnet stepper motor according to claim 7, characterized in that: The bidirectional cam is made of a beryllium copper alloy with high conductivity, and conductive collector rings are provided at both ends of its axial direction to guide the induced current on the rotating shaft into the electrical measurement shielding shell through conductive grease.

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