Magnetic powder brake synchronous mechanism for electric drive axle off-line NVH running-in and test method

Abstract

The application discloses a kind of magnetic powder brake synchronous mechanism and test method of electric drive bridge off-line NVH running-in, it is related to automobile accessory testing technical field, mechanism contains two groups of symmetrical synchronous units and length adjusting assembly, unit contains bottom plate, loading connecting shaft, synchronous transmission assembly, tensioning mechanism and transmission shaft, loading connecting shaft is connected with transmission assembly and magnetic powder brake, tensioning mechanism abuts transmission belt.When testing, adjust the distance between synchronous units, butt joint hub, arrange sensor and set parameter, drive operation and load;Unit restricts the synchronous speed of both ends, collects vibration noise data;After grading running-in, frequency domain data is analyzed, differential interference noise and defect characteristics are distinguished, defects are judged and report is output.The application solves the problem that when magnetic powder brake is loaded, due to the limited torque accuracy, differential effect is generated in differential, irregular vibration noise is generated to cover defects, and the accuracy of NVH detection is affected.

Description

Technical Field

[0001] This invention relates to the field of automotive parts testing technology, and in particular to a magnetic powder brake synchronization mechanism and testing method for NVH break-in of an electric drive axle. Background Technology

[0002] The axle is a crucial component of the automotive transmission system, consisting of important parts such as the axle housing, motor, reducer, half-shafts, and wheel hubs. With increasing market demands for smoothness and low noise levels in vehicles, abnormal noises such as whistling and slamming during operation of the electric drive axle have become key control indicators for off-line testing. Therefore, electric drive axles require break-in testing on a test bench before production, and NVH (Noise, Vibration, and Harshness) testing systems are used to monitor their vibration and noise levels. Common drive solutions for existing off-line testing benches include: 1) using an MCU-driven motor to provide speed or torque, with a dynamometer applied to both wheels to simulate load conditions; however, this solution uses expensive dynamometers. 2) using an MCU-driven motor to provide speed, with magnetic powder brakes at both wheels to simulate load conditions; this solution is cheaper, but the torque accuracy of magnetic powder brakes is limited, which can cause differential effects in the gearbox differential, leading to irregular vibrations and noise in the electric drive axle during operation. This can mask some gear and bearing defects, affecting the accuracy of NVH test results. Summary of the Invention

[0003] The purpose of this invention is to solve the problem that when the existing electric drive axle off-line test bench uses a magnetic powder brake for loading, the limited torque accuracy causes the reducer differential to produce a differential effect, resulting in irregular vibration and noise during the operation of the electric drive axle, which masks some gear and bearing defects and affects the accuracy of NVH test results. The invention provides a magnetic powder brake synchronization mechanism and test method for NVH break-in of electric drive axles that is simple in structure, has good applicability, and is inexpensive.

[0004] To solve the above problems, the technical solution adopted by the present invention is as follows: On one hand, the present invention provides a magnetic powder brake synchronization mechanism for NVH break-in of an electric drive axle, comprising two symmetrically arranged synchronization units and a length adjustment assembly connecting the two synchronization units. The length adjustment assembly is fixedly connected between the opposite ends of the drive shafts of the two synchronization units. Each synchronization unit includes a fixed base plate, a loading connecting shaft, a synchronization transmission assembly, a belt tensioning mechanism, a drive shaft, and a drive shaft support assembly. Each fixed base plate is slidably connected to the loading end on the corresponding side of the test bench. One end of each loading connecting shaft is connected to the rotary output end of the magnetic powder brake, and the other end is connected to one end of the drive shaft on the corresponding side through the synchronization transmission assembly. The drive shaft support assembly is fixedly installed on the fixed base plate, and the drive shaft is rotatably inserted through the drive shaft support assembly. The belt tensioning mechanism is disposed on one side of the synchronization transmission assembly and abuts against the outside of the transmission belt of the synchronization transmission assembly.

[0005] In the above-mentioned technical solution of the magnetic powder braking synchronization mechanism for NVH break-in of the electric drive axle, a more specific technical solution can also be: the length adjustment component includes a hollow polygonal cylinder and a solid polygonal rod, the solid polygonal rod is inserted into the hollow polygonal cylinder and the two are clearance-fitted, and the opposite ends of the hollow polygonal cylinder and the solid polygonal rod are respectively fixedly connected to the corresponding drive shaft.

[0006] In some possible implementations, the drive shaft support assembly includes a bearing housing disposed on the fixed base plate and a self-aligning roller bearing installed in the bearing housing. The fixed base plate has a positioning groove extending axially along the drive shaft. The bearing housing is fixedly installed in the positioning groove, and the drive shaft passes through the inner ring of the self-aligning roller bearing.

[0007] In some possible implementations, the synchronous transmission assembly includes arc-tooth synchronous pulleys and a synchronous belt, with the arc-tooth synchronous pulleys fixedly sleeved on the loading connecting shaft and the transmission shaft respectively, and the synchronous belt sleeved on the outer periphery of the two arc-tooth synchronous pulleys.

[0008] In some possible implementations, the belt tensioning mechanism includes a fixed plate, a fixed block, an adjusting slider, a fixed rod, an adjusting wheel, and an adjusting bolt. The fixed plate is fixed to the fixed base plate, the fixed block is fixed to the fixed plate, and the adjusting slider is slidably disposed on the fixed plate and on the same side as the fixed block. The fixed plate has an elongated groove extending along the tension adjustment direction of the synchronous belt. The fixed rod passes through the elongated groove, the adjusting wheel is fixedly connected to the adjusting slider through the fixed rod, the adjusting wheel abuts against the outer side of the synchronous belt, and the adjusting bolt passes through the fixed block and is threadedly connected to the adjusting slider.

[0009] In some possible implementations, the loading connecting shaft is provided with a stepped positioning platform and a retaining spring groove, and the arc-tooth synchronous pulley is axially limited by the stepped positioning platform and the retaining spring; a keyway is opened at the end of the loading connecting shaft, and a flat key is assembled in the keyway to circumferentially lock the rotating output end of the magnetic powder brake.

[0010] In some possible implementations, a bracket is fixedly installed on one side of the magnetic powder brake, and the loading connecting shaft passes through the bracket after exiting the magnetic powder brake; the loading connecting shaft is connected to the wheel end connecting fixture via a universal drive shaft, and the wheel end connecting fixture is positioned and docked with the wheel hub assembly.

[0011] On the other hand, the present invention provides a test method for the NVH break-in of an electric drive axle, which uses the aforementioned magnetic powder braking synchronization mechanism and includes the following steps: S1. Fix the electric drive bridge assembly under test on the test bench; adjust the distance between the two sets of synchronous units by sliding the fixed base plates on both sides, and adjust the telescopic cooperation stroke of the hollow polygonal cylinder and solid polygonal rod of the length adjustment component to match the installation distance at both ends of the electric drive bridge assembly under test; the wheel hub assemblies at both ends of the electric drive bridge assembly under test are synchronously connected to the loading connection shaft of the two sets of synchronous units through the universal drive shaft tooling. S2. Install NVH sensors on the electric drive bridge assembly under test and set the bench MCU break-in control parameters. S3, the bench MCU outputs control signals to drive the electric drive bridge assembly under test to operate, and the magnetic powder brake outputs braking load; two sets of synchronization units constrain the speed of the two wheel ends of the electric drive bridge assembly under test to be synchronized, and the NVH acquisition component collects vibration and noise data throughout the break-in process; S4. After the graded break-in is completed, analyze the vibration and noise frequency domain data, distinguish the characteristic noise of gear and bearing defects, determine whether there are defects in the electric drive axle assembly under test, and output the test results. S5, the magnetic powder brake unload torque, the bench MCU sends a speed reduction and stop control command, stores the test data and generates a test report.

[0012] In the above-mentioned test method for NVH break-in of electric drive axle, a more specific technical solution may be: in step S3, the magnetic powder brake is loaded with multi-stage incremental torque, and the bench MCU outputs control commands in multi-stage speed segments, so that the electric drive axle assembly under test goes through different differential speed conditions to expose defect characteristics and complete the graded break-in.

[0013] In some possible implementations, in step S4, the acquired time-domain signal is converted into a frequency-domain signal, and the characteristic noise of gear and bearing defects is distinguished according to the gear meshing order and bearing characteristic frequency. The defect characteristic frequency component is used to determine whether there is a defect in the electric drive bridge assembly under test.

[0014] By adopting the above technical solution, the present invention has the following advantages compared with the prior art: 1. This synchronization mechanism is equipped with two sets of symmetrical synchronization units and a length adjustment component. The synchronization unit integrates a fixed base plate, a loading connecting shaft, a synchronization transmission component, a belt tensioning mechanism, a transmission shaft, and a support component. The loading connecting shaft connects to the magnetic powder brake of the existing test bench and is linked to the transmission shaft through the synchronization transmission component. The tensioning mechanism presses the transmission belt, and the dual synchronization units force the wheel end speeds to be synchronized, eliminating differential speed interference noise caused by the magnetic powder brake and preventing gear and bearing defects from being masked. The fixed base plate with the length adjustment component can be adapted to electric drive bridges with different wheelbases. The modular structure can directly modify the existing magnetic powder test bench, saving the investment in a high-priced dynamometer. The synchronization transmission and tensioning structure avoid slippage, ensuring the repeatability of test data. The components are also easy to disassemble and maintain on the production line.

[0015] 2. The length adjustment component uses hollow polygonal cylinder and solid polygonal rod to telescopically extend and connect to the drive shafts on both sides. The telescopic structure can be steplessly adapted to electric drive bridges of different lengths. The polygonal shape forms an anti-rotation structure, ensuring that torque and speed are transmitted synchronously during the extension and retraction process. The polygonal cross section has high torsional and bending stiffness, is not easily deformed under heavy load break-in, and maintains synchronization accuracy over a long period of time.

[0016] 3. The fixed base plate has a positioning groove, and the bearing housing can slide along the groove. The internal assembly of the self-aligning roller bearing supports the drive shaft. The sliding bearing housing can quickly calibrate the coaxiality of the drive shaft, shortening the changeover and debugging time. The self-aligning roller bearing can compensate for the shaft's own weight and the shaft center offset caused by assembly, reducing synchronization error and bearing wear. The double bearing support reduces the drive shaft runout and avoids the vibration and noise of the mechanism itself interfering with NVH acquisition. The bearing housing can be slidably disassembled for easy replacement and maintenance of parts.

[0017] 4. The synchronous transmission component uses a circular arc tooth synchronous belt pulley to connect the loading shaft and the transmission shaft. The circular arc teeth mesh without slippage, accurately transmit the speed and maintain the synchronization of the wheel ends. The large tooth surface contact area can bear the large torque during the break-in period, making it less prone to tooth skipping and failure. The meshing impact is small, and the self-added noise is low and does not interfere with the test. The fixed number of teeth forms a constant transmission ratio, and there is no speed drift during long-term mass production, which stably ensures the repeatability accuracy of the test.

[0018] 5. The belt tensioning mechanism consists of a fixed vertical plate, an adjusting slider, an adjusting wheel, and adjusting bolts. The adjusting wheel is pushed by the bolt feed to press the synchronous belt, which can accurately match the tension of the synchronous belt and prevent slippage or excessive wear. After debugging, the locking slider locks the tension. The transmission is stable throughout the mass production process. The single-sided arrangement of the mechanism does not interfere with the tooling docking process. The slider and groove direct-drive structure makes it easy to disassemble and assemble the synchronous belt, which can effectively improve the efficiency of parts changeover on the production line.

[0019] 6. The loading connection shaft is equipped with a stepped positioning platform and a snap ring groove to limit the synchronous pulley. The end keyway is matched with a flat key and a magnetic powder brake for locking. The double limit of the step and snap ring prevents the pulley from axially moving and losing teeth. The flat key realizes zero-slip torque transmission, ensuring synchronous load on both sides. The stepped structure simplifies assembly and positioning, reduces human error, and the shaft is evenly stressed and not easily damaged, thus extending the service life of the equipment.

[0020] 7. The bracket provides stable radial support to the through-load connection shaft, reducing high-speed rotational runout of the shaft and minimizing additional vibration and noise interference with NVH testing; the universal drive shaft can compensate for assembly coaxial deviations, and the tooling precisely positions the hub, ensuring smooth and synchronous transmission of torque and speed.

[0021] 8. This testing method sequentially completes the entire process of tooling adaptation, NVH sensor placement, bench MCU speed control loading synchronous acquisition, frequency domain noise analysis, and shutdown for evidence storage. It eliminates the differences in manual assembly through standardized assembly steps, uses multi-point sensors to eliminate base noise, and utilizes a synchronization mechanism to eliminate differential speed interference. The acquired signals only reflect the true defects of the parts, and frequency domain analysis distinguishes noise types to achieve accurate defect determination. Automatic data storage generates reports to meet quality traceability requirements. The entire process can be adapted to a low-cost magnetic particle bench by simply adding a synchronization mechanism, without the need to purchase an expensive dynamometer.

[0022] 9. The magnetic powder brake is used to increase torque in multiple stages, and the bench MCU is used to control the speed in multiple stages. The graded loading can simulate the entire driving conditions, fully expose the hidden defects of the gear bearings, and avoid impact damage to the qualified electric drive axle by loading in stages. The vibration and noise are collected under different working conditions to locate the defects corresponding to the driving conditions. At the same time, the synchronization mechanism is fully verified to ensure the stability of the synchronization constraint under high and low speeds and light and heavy loads.

[0023] 10. By converting the time-domain signal to the frequency domain and combining the order and characteristic frequency to distinguish noise, and using the synchronization mechanism to eliminate differential noise, interference noise and component defect signals can be clearly distinguished, avoiding misjudgment and accurately identifying gear and bearing faults. The test data can be stored for quality traceability and process optimization. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the magnetic powder braking synchronization mechanism during the NVH break-in process of the electric drive axle.

[0025] Figure 2 This is a schematic diagram showing the usage status of the magnetic powder brake synchronization mechanism during the NVH break-in process of this electric drive axle.

[0026] Figure 3 This is a schematic diagram of the belt tensioning mechanism.

[0027] Figure 4 This is a schematic diagram of the connection structure of the length adjustment component.

[0028] Figure 5 This is a schematic diagram showing the connection between the loading connecting shaft and the connecting hole inside the magnetic powder brake.

[0029] Figure 6 yes Figure 5 A diagram from another perspective.

[0030] Explanation of the numbering in the diagram: 1. Synchronization unit; 1-1. Fixed base plate; 1-11. Mounting hole; 1-12. Lifting lug; 1-13. Positioning slot; 1-2. Loading connecting shaft; 1-21. Stepped positioning platform; 1-22. Keyway; 1-23. Snap ring slot; 1-3. Synchronization transmission assembly; 1-31. Arc toothed synchronous pulley; 1-32. Synchronous belt; 1-4. Drive shaft; 1-5. Drive shaft support assembly; 1-51. Bearing housing; 1-52. Self-aligning roller bearing; 1-53. Bearing cover plate ; 1-6, belt tensioning mechanism; 1-61, fixed upright plate; 1-611, long strip slide; 1-62, fixing block; 1-63, adjusting slider; 1-64, fixing rod; 1-65, adjusting wheel; 1-66, adjusting bolt; 2, length adjustment assembly; 2-1, hollow hexagonal square steel; 2-2, solid hexagonal square steel; 3, magnetic powder brake; 4, bracket; 5, electric drive bridge assembly under test; 5-1, hub assembly; 6, wheel end connection fixture; 7, universal drive shaft; 8, stand; 8-1, slide rail. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments: Figure 1 and Figure 2 The magnetic powder brake synchronization mechanism shown is used for the NVH break-in of the electric drive axle. When installed on an existing magnetic powder brake test bench, it can force the speed of the two wheels of the electric drive axle under test to be synchronized. The synchronization mechanism includes two symmetrically arranged synchronization units 1 and a length adjustment component 2 connecting the two synchronization units 1. The two synchronization units 1 are mounted on the sliders of the slide rails 8-1 on the left and right sides of the stand 8 via the fixed base plate 1-1 at their bottom. When the product is being changed and debugged, they can move along the slide rail 8-1 to adapt to electric drive bridge assemblies with different wheelbase specifications. After the wheelbase is adjusted, the fixed base plate 1-1 is locked to complete the positioning. One end of the loading connection shaft 1-2 of each of the two synchronization units 1 is connected to the rotation output end of the corresponding magnetic powder brake 3, and the other end is connected to the wheel hub assemblies 5-1 at both ends of the electric drive bridge assembly through the universal drive shaft 7 and the tooling to complete the synchronous transmission connection between the two wheel ends of the electric drive bridge and the magnetic powder brake 3. The length adjustment component 2 is fixedly connected between the opposite ends of the drive shafts 1-4 of the two synchronization units 1. On the one hand, it can extend and retract to adjust the total length to adapt to electric drive bridges with different wheelbases. On the other hand, it relies on the multi-sided cooperation structure to prevent rotation and synchronously transmit the torque and speed of the drive shafts 1-4 on both sides, and together with the two synchronization units 1, it constrains the two wheel ends of the electric drive bridge to rotate synchronously.

[0032] The synchronization unit 1 includes a fixed base plate 1-1, a loading connecting shaft 1-2, a synchronization transmission assembly 1-3, a belt tensioning mechanism 1-6, a transmission shaft 1-4, and a transmission shaft support assembly 1-5. Each fixed base plate 1-1 is slidably connected to the loading end on the corresponding side of the test bench 8, allowing the synchronization unit 1 to slide along the slide rail 8-1 to adjust the spacing between the two sets of synchronization units 1. The fixed base plate 1-1 is designed according to the base plate structure of the magnetic powder brake 3 and the slide rail 8-1 and slider structure of the loading end of the test bench 8, so that the magnetic powder brake 3 is fixed on the fixed base plate 1-1. In this embodiment, the fixed base plate 1-1 is provided with mounting holes 1-11, through which the magnetic powder brake 3 is fixed to the fixed base plate 1-1, allowing the magnetic powder brake 3 and the synchronization unit 1 to move as a whole, adapting to different electric drive bridges without separate disassembly and assembly, thus shortening the debugging time. The bottom of the fixed base plate 1-1 is equipped with a positioning structure that mates with the slider of the slide rail 8-1. It is locked to the slide rail slider via a flat key to prevent the fixed base plate 1-1 from shifting during break-in vibration, ensuring the positioning accuracy of the left and right loading ends. All components are integrated into a single fixed base plate, allowing for modular assembly and disassembly. Existing magnetic powder braking platforms can be directly added or modified without replacing the entire equipment. The fixed base plate 1-1 is also equipped with lifting lugs 1-12, facilitating the lifting and disassembly of the synchronization unit 1 and production line changeover operations. The magnetic powder brake 3 is directly fixed to the fixed base plate 1-1, eliminating the need for additional supports, reducing modification costs. The standardized sliding structure can be directly added to existing magnetic powder platforms, offering strong versatility.

[0033] The synchronous transmission assembly 1-3 includes arc-tooth synchronous pulleys 1-31 and a synchronous belt 1-32. Arc-tooth synchronous pulleys 1-31 are fixedly sleeved on the loading connecting shaft 1-2 and the transmission shaft 1-4, respectively. The synchronous belt 1-32 is sleeved on the outer circumference of the two arc-tooth synchronous pulleys 1-31, realizing the synchronous transmission of speed and torque. The arc-tooth synchronous pulleys 1-31 with an appropriate number of teeth can be selected according to the magnitude of the loading torque and the maximum speed. The arc-tooth synchronous pulleys 1-31 are positioned by the stepped position of the shaft and the retaining ring groove 1-23, ensuring reliable axial fixation of the pulleys and preventing displacement during operation.

[0034] One end of each loading connecting shaft 1-2 is connected to the rotary output end of the magnetic powder brake 3, and the other end is connected to one end of the corresponding transmission shaft 1-4 via the synchronous transmission assembly 1-3. For example... Figure 5 , Figure 6As shown, the loading connecting shaft 1-2 is designed according to the size of the rotating shaft hole inside the magnetic powder brake 3. The connecting hole inside the magnetic powder brake 3 has a keyway, and a corresponding keyway 1-22 is opened at the end of the loading connecting shaft 1-2. A flat key is installed in the keyway 1-22 and circumferentially locks with the rotating output end of the magnetic powder brake 3 to achieve anti-rotation and torque transmission. The loading connecting shaft 1-2 is also equipped with a stepped positioning platform 1-21 and a retaining ring groove 1-23. The arc-tooth synchronous pulley 1-31 is axially limited by the stepped positioning platform 1-21 and the retaining ring to prevent the synchronous pulley from axially moving and losing teeth. After the loading connecting shaft 1-2 is connected to the arc-tooth synchronous pulley 1-31, the rotational speed input to the magnetic powder brake 3 is transmitted to the loading connecting shaft 1-2 through the flat key, and then output through the arc-tooth synchronous pulley 1-31. A bracket 4 is also fixedly installed on one side of the magnetic powder brake 3. The bracket 4 is a frame structure with relatively arranged double-layer walls. The loading connecting shaft 1-2, which passes through the magnetic powder brake 3, passes through the two layers of walls in sequence. An angular contact ball bearing is assembled between the wall and the loading connecting shaft 1-2 to form a rotational fit. The double-layer wall combined with the angular contact ball bearing can form a stable radial support for the loading connecting shaft, reduce the radial runout of the shaft at high speed, and reduce the interference of the equipment's own vibration on NVH detection. The end of the loading connecting shaft 1-2 away from the magnetic powder brake 3 is connected to the wheel end connecting fixture 6 through the universal drive shaft 7. The wheel end connecting fixture 6 can be precisely positioned and docked with the wheel hub assembly 5-1 of the electric drive bridge assembly 5 under test by relying on the wheel rim stop. The universal drive shaft 7 can compensate for the coaxial deviation caused by the assembly and ensure that the torque and speed are transmitted to the wheel end smoothly and synchronously.

[0035] The drive shaft support assembly 1-5 is fixedly installed on the fixed base plate 1-1, and the drive shaft 1-4 is rotatably inserted through the drive shaft support assembly 1-5. Figure 2 As shown, the drive shaft support assembly 1-5 includes a bearing housing 1-51 disposed on the fixed base plate 1-1 and self-aligning roller bearings 1-52 installed within the bearing housing 1-51. Preferably, two self-aligning roller bearings 1-52 are mounted on the drive shaft 1-4, with the two bearings installed within the bearing housing 1-51, and then a bearing cover plate 1-53 is installed to ensure the bearing operating environment. The self-aligning roller bearings 1-52 can eliminate minor shaft center misalignment caused by assembly and the weight of the long shaft, effectively compensating for shaft center misalignment caused by the shaft's weight and assembly, reducing synchronization errors and bearing wear. The dual bearing support reduces drive shaft runout and avoids interference from the mechanism's own vibration noise with NVH data acquisition. In addition, the fixed base plate 1-1 has a positioning groove 1-13 extending axially along the drive shaft 1-4, and the bearing housing 1-51 is fixedly installed within the positioning groove 1-13; during model changeover, the bearing housing 1-51 can slide along the groove, shortening the model changeover and debugging time.

[0036] like Figure 4As shown, the length adjustment component 2 includes a hollow polygonal cylinder and a solid polygonal rod. In this embodiment, the hollow polygonal cylinder is made of hollow hexagonal square steel 2-1, and the solid polygonal rod is made of solid hexagonal square steel 2-2. Both are standard parts and can be purchased directly. The solid hexagonal square steel 2-2 passes through the hollow hexagonal square steel 2-1 with a clearance fit, allowing both to extend and retract freely, thus adjusting the length of the left and right loading ends. Simultaneously, their hexagonal structure forms an anti-rotation structure, ensuring the continuous synchronous transmission of speed and torque during extension and retraction. The opposite ends of the hollow hexagonal square steel 2-1 and the solid hexagonal square steel 2-2 are welded and fixedly connected to the corresponding drive shafts 1-4. In other embodiments, the hollow polygonal cylinder and the solid polygonal rod can also adopt other polygonal cross-sectional shapes such as four-sided or octagonal, as long as the extension and anti-rotation functions can be achieved. Hexagonal square steel has high torsional and bending stiffness, is not easily deformed under heavy load break-in, and can maintain synchronization accuracy for a long time.

[0037] like Figure 3 As shown, the belt tensioning mechanism 1-6 is located on one side of the synchronous transmission assembly 1-3 and abuts against the outside of the synchronous belt 1-32 of the synchronous transmission assembly 1-3. The belt tensioning mechanism 1-6 includes a fixed upright plate 1-61, a fixed block 1-62, an adjusting slider 1-63, a fixed rod 1-64, an adjusting wheel 1-65, and an adjusting bolt 1-66. The fixed upright plate 1-61 is fixed to the fixed base plate 1-1, the fixed block 1-62 is fixed to the fixed upright plate 1-61, and the adjusting slider 1-63 is slidably disposed on the fixed upright plate 1-61 and on the same side as the fixed block 1-62. The fixed plate 1-61 has a long groove 1-611 extending along the tension adjustment direction of the synchronous belt 1-32. A fixing rod 1-64 passes through the long groove 1-611. The adjusting wheel 1-65 is fixedly connected to the adjusting slider 1-63 via the fixing rod 1-64. The adjusting wheel 1-63 abuts against the outer side of the synchronous belt 1-32. An adjusting bolt 1-66 passes through the fixed block 1-62 and is threadedly connected to the adjusting slider 1-63. During adjustment, the adjusting slider 1-63 can slide on the fixed plate 1-61. Rotating the adjusting bolt 1-66 on the fixed block 1-62 pushes the adjusting slider 1-63, causing the adjusting wheel 1-65 to press against the synchronous belt 1-32, thus achieving belt tension. After adjustment, the adjusting slider 1-63 is locked with bolts to ensure stable tension, prevent slippage or excessive wear, and ensure stable transmission throughout mass production.

[0038] This embodiment uses the test method of the above-mentioned magnetic particle braking synchronization mechanism, including the following steps: S1. Hoist and fix the待测 electric drive bridge assembly 5 on the test bench 8; Slide the fixed bottom plates 1-1 on both sides to move the two sets of synchronization units 1 along the slide rails of the test bench 8, and adjust the distance between the two sets of synchronization units 1; At the same time, adjust the telescopic fit stroke between the hollow hexagonal steel 2-1 and the solid hexagonal steel 2-2 of the length adjustment component 2 so that the distance between the two sets of synchronization units 1 matches the installation distance at both ends of the待测 electric drive bridge assembly 5. The hub assemblies 5-1 at the left and right ends of the待测 electric drive bridge assembly 5 are positioned by the rim stop of the wheel end connection tooling 6 and fixed with tire nuts, and then synchronously docked with the loading connection shafts 1-2 of the two sets of synchronization units 1 through the universal drive shaft 7.

[0039] S2. Arrange NVH sensors on the待测 electric drive bridge assembly 5; Arrange a vibration sensor on the housing near the bearing position of the reduction gearbox assembly, and also arrange a vibration sensor on the housing near the bearing position of the motor assembly. Place a microphone sensor 500 mm away from the bridge assembly 5 to simultaneously collect the vibration values and noise values of the reduction gearbox assembly and the motor assembly; Set the running-in control parameters of the test bench MCU, including parameters such as the target speed and the loading torque. The NVH test software can select Siemens LMSTestlab or other equivalent software. In this method, the test bench MCU is the main controller supporting the test bench, used to uniformly control the running-in speed, the loading torque of the magnetic particle brake, the start and stop of the whole machine, and the linkage of NVH acquisition.

[0040] S3. The test bench MCU outputs a control signal to drive the待测 electric drive bridge assembly 5 to operate; Start the magnetic particle brake 3, select the required torque value, and the magnetic particle brake 3 outputs a braking load to simulate the driving load condition. The two sets of synchronization units 1, through the transmission of the circular arc tooth synchronous belt pulleys 1-31, the synchronous belt 1-32, the transmission shaft 1-4 and the length adjustment component, constrain the rotational speeds of the two wheel ends of the待测 electric drive bridge assembly 5 to be synchronous, ensuring that the differential of the reduction gearbox does not produce a differential effect and eliminating the irregular vibration noise caused by the limited accuracy of the magnetic particle braking torque. The NVH acquisition component collects the vibration and noise data during the running-in process throughout. Preferably, the magnetic particle brake 3 is loaded with multi-segment increasing torque, and the test bench MCU outputs control instructions in multi-level speed segments, so that the待测 electric drive bridge assembly 5 traverses different differential conditions to expose defect characteristics and complete hierarchical running-in. It can be loaded step by step in the order of low speed and low torque, medium speed and medium torque, and high speed and high torque, so that components such as gears and bearings are fully run-in under different working conditions, and hidden defects are exposed under specific working conditions. At the same time, step-by-step loading can avoid impact damage to qualified electric drive bridge assemblies.

[0041] S4. After the graded break-in period, the vibration and noise frequency domain data are analyzed using NVH testing software. The collected time-domain signals are converted into frequency-domain signals, and the characteristic noise of gear and bearing defects is distinguished based on the gear meshing order and bearing characteristic frequencies. Since the synchronization mechanism has eliminated the irregular vibration noise caused by the differential effect at the source, the repeatability error of the vibration amplitude of the differential gear meshing order in the frequency domain spectrum is extremely small. The characteristic frequency components corresponding to gear and bearing defects can be clearly displayed, thus accurately determining whether there are manufacturing or assembly defects in the gears, bearings, and other components of the electric drive axle assembly under test, and outputting the test results.

[0042] S5. After the test is completed, the magnetic powder brake 3 unloads the torque, and the bench MCU issues a speed reduction and shutdown control command to smoothly stop the electric drive axle assembly. The test data is stored and a test report is automatically generated. The test report includes information such as vibration and noise time-domain waveforms, frequency domain analysis spectra, and defect judgment conclusions, meeting the quality traceability requirements.

[0043] In other embodiments, the break-in strategy using multi-stage incremental torque loading and multi-level speed segmented control in step S3 can be replaced with other loading modes such as constant torque and constant speed break-in or sinusoidal torque loading, as long as the electric drive axle assembly can be operated under load and NVH data can be collected. The number and location of vibration sensors are not limited to the above embodiments. Sensor measuring points can be added or adjusted according to actual detection needs. For example, vibration measuring points can be added to the differential housing, half-shaft bearing housing, etc., to obtain more comprehensive vibration data.

[0044] In the break-in testing of electric drive axle assemblies, compared to the expensive dynamometer-based loading test bench, this invention provides a cost-effective mechanism and method for achieving speed synchronization and torque loading at both wheel ends of the electric drive axle assembly using a magnetic powder brake. After adopting the mechanism and method of this invention, no abnormal noise caused by the differential effect was subjectively audible. The NVH testing software monitored the vibration value repeatability error of the differential gear meshing order of the axle assembly during the testing process, which was ±0.02g, and the noise value repeatability error was ±0.3dB, completely eliminating the differential effect and effectively ensuring the accuracy of the NVH test results. The synchronization mechanism and testing method of this invention have been practically used on the applicant's production line break-in test bench with a magnetic powder brake, verifying its feasibility and effectiveness, and fully meeting the NVH quality control requirements for electric drive axle assembly leaving the factory.

[0045] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnetic powder braking synchronization mechanism for NVH break-in of an electric drive axle, characterized in that: The system includes two symmetrically arranged synchronization units and a length adjustment assembly connecting the two synchronization units. The length adjustment assembly is fixedly connected between the opposite ends of the drive shafts of the two synchronization units. Each synchronization unit includes a fixed base plate, a loading connecting shaft, a synchronization transmission assembly, a belt tensioning mechanism, a drive shaft, and a drive shaft support assembly. Each fixed base plate is slidably connected to the loading end on the corresponding side of the platform. One end of each loading connecting shaft is connected to the rotary output end of a magnetic powder brake, and the other end is connected to one end of the drive shaft on the corresponding side through the synchronization transmission assembly. The drive shaft support assembly is fixedly installed on the fixed base plate, and the drive shaft rotatably passes through the drive shaft support assembly. The belt tensioning mechanism is located on one side of the synchronous transmission assembly and abuts against the outside of the transmission belt of the synchronous transmission assembly.

2. The magnetic powder braking synchronization mechanism for NVH break-in of the electric drive axle according to claim 1, characterized in that: The length adjustment assembly includes a hollow polygonal cylinder and a solid polygonal rod. The solid polygonal rod passes through the hollow polygonal cylinder and the two are fitted with a clearance. The opposite ends of the hollow polygonal cylinder and the solid polygonal rod are respectively fixedly connected to the corresponding drive shaft.

3. The magnetic powder braking synchronization mechanism for NVH break-in of the electric drive axle according to claim 1, characterized in that: The drive shaft support assembly includes a bearing housing disposed on the fixed base plate and a self-aligning roller bearing installed in the bearing housing. The fixed base plate has a positioning groove extending along the axial direction of the drive shaft. The bearing housing is fixedly installed in the positioning groove, and the drive shaft passes through the inner ring of the self-aligning roller bearing.

4. The magnetic powder braking synchronization mechanism for NVH break-in of the electric drive axle according to claim 1, characterized in that: The synchronous transmission assembly includes arc-tooth synchronous pulleys and a synchronous belt. The arc-tooth synchronous pulleys are fixedly sleeved on the loading connecting shaft and the transmission shaft, respectively, and the synchronous belt is sleeved on the outer periphery of the two arc-tooth synchronous pulleys.

5. The magnetic powder braking synchronization mechanism for NVH break-in of the electric drive axle according to claim 4, characterized in that: The belt tensioning mechanism includes a fixed plate, a fixed block, an adjusting slider, a fixed rod, an adjusting wheel, and an adjusting bolt. The fixed plate is fixed to the fixed base plate, the fixed block is fixed to the fixed plate, and the adjusting slider is slidably disposed on the fixed plate and on the same side as the fixed block. The fixed plate has an elongated groove extending along the tension adjustment direction of the synchronous belt. The fixed rod passes through the elongated groove, and the adjusting wheel is fixedly connected to the adjusting slider through the fixed rod. The adjusting wheel abuts against the outer side of the synchronous belt, and the adjusting bolt passes through the fixed block and is threadedly connected to the adjusting slider.

6. The magnetic powder braking synchronization mechanism for NVH break-in of the electric drive axle according to claim 1, characterized in that: The loading connecting shaft is provided with a stepped positioning platform and a retaining spring groove. The arc toothed synchronous belt pulley is axially limited by the stepped positioning platform and the retaining spring. A keyway is opened at the end of the loading connecting shaft, and a flat key is installed in the keyway to lock the magnetic powder brake rotation output end circumferentially.

7. The magnetic powder braking synchronization mechanism for NVH break-in of the electric drive axle according to claim 1, characterized in that: A bracket is fixedly installed on one side of the magnetic powder brake, and the loading connecting shaft passes through the bracket after exiting the magnetic powder brake; the loading connecting shaft is connected to the wheel end connecting fixture through a universal drive shaft, and the wheel end connecting fixture is positioned and docked with the wheel hub assembly.

8. A test method for NVH break-in of an electric drive axle, employing the magnetic powder braking synchronization mechanism as described in any one of claims 1 to 7, characterized in that... Includes the following steps: S1. Fix the electric drive bridge assembly under test on the test bench; adjust the distance between the two sets of synchronous units by sliding the fixed base plates on both sides, and adjust the telescopic cooperation stroke of the hollow polygonal cylinder and solid polygonal rod of the length adjustment component to match the installation distance at both ends of the electric drive bridge assembly under test; the wheel hub assemblies at both ends of the electric drive bridge assembly under test are synchronously connected to the loading connection shaft of the two sets of synchronous units through the universal drive shaft tooling. S2. Install NVH sensors on the electric drive bridge assembly under test and set the bench MCU break-in control parameters. S3, the bench MCU outputs control signals to drive the electric drive bridge assembly under test to operate, and the magnetic powder brake outputs braking load; two sets of synchronization units constrain the speed of the two wheel ends of the electric drive bridge assembly under test to be synchronized, and the NVH acquisition component collects vibration and noise data throughout the break-in process; S4. After the graded break-in is completed, analyze the vibration and noise frequency domain data, distinguish the differential interference noise from the characteristic noise of gear and bearing defects, determine whether there are defects in the electric drive axle assembly under test, and output the test results. S5, the magnetic powder brake unload torque, the bench MCU sends a speed reduction and stop control command, stores the test data and generates a test report.

9. The test method for NVH break-in of electric drive axles according to claim 8, characterized in that: In step S3, the magnetic powder brake is loaded with multi-stage incremental torque, and the bench MCU outputs control commands in stages with multi-level speeds, so that the electric drive bridge assembly under test goes through different differential speed conditions to expose defect characteristics and complete the graded break-in.

10. The test method for NVH break-in of electric drive axles according to claim 8, characterized in that: In step S4, the collected time-domain signal is converted into a frequency-domain signal. Based on the gear meshing order and bearing characteristic frequency, the characteristic noise of gear and bearing defects is distinguished. The defect characteristic frequency component is used to determine whether there are defects in the electric drive bridge assembly under test.

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