Method and machine for testing grease wear life of driving shaft

Abstract

The invention relates to a driving shaft grease wear life test method and a test machine, and relates to the technical field of grease tests, the method comprises the following steps: road load spectrum generation: collecting working condition data of a driving shaft in real vehicle driving, and converting the working condition data into a time domain load spectrum which can be loaded by a bench test machine; initial vibration benchmark testing: installing the driving shaft assembly to be tested on an NVH testing machine through a hub bearing connecting tool; loading the time domain load spectrum, and collecting an initial vibration amplitude and a spectrum characteristic through an acceleration sensor; performing segmented mileage durability simulation: transferring the driving shaft assembly to a road spectrum testing machine, and performing segmented simulation on driving durability according to a preset mileage; re-testing segmented vibration: returning the driving shaft assembly to the NVH testing machine to re-test vibration amplitude and frequency spectrum characteristics under the same time domain load spectrum after each period of preset mileage durability is completed; and grease performance analysis: analyzing the grease state based on the change of the vibration amplitude and the spectrum characteristics. The method has the effect of improving the test efficiency.

Description

TECHNICAL FIELD

[0001] The application relates to a grease test method, in particular to a test method and a test machine for the service life of driving shaft grease. BACKGROUND

[0002] About 60% of the failures of constant velocity driving shaft assembly products after sales are related to NVH and grease wear life performance. With the increasing demand of automobile manufacturers for solutions to the NVH and grease application problems of constant velocity joints in recent years, the time is more and more compressed, and the previous vehicle verification method led by automobile manufacturers cannot meet the extreme pursuit of efficiency and cost, and it is urgent to have independent verification capability by driving shaft assembly suppliers.

[0003] The automobile shakes after driving for a certain distance, and the variable cannot be accurately understood during the process. The troubleshooting and improvement verification can only be realized by a real vehicle, and professional test drivers need to perform multiple real vehicle verifications, which is relatively complex and has a very long verification cycle, resulting in high cost. SUMMARY

[0004] The purpose of the application is to provide a test method for the service life of driving shaft grease, which can improve test efficiency and reduce test cost.

[0005] In a first aspect, the application provides a test method for the service life of driving shaft grease, which adopts the following technical scheme:

[0006] The test method for the service life of driving shaft grease comprises the following steps:

[0007] S1 Road load spectrum generation: collecting working condition data of the driving shaft in the real vehicle driving and converting the data into a time domain load spectrum that can be loaded on a bench test machine;

[0008] S2 Initial vibration reference test: installing the driving shaft assembly to be tested on an NVH test machine through a wheel hub bearing connecting tool; loading the time domain load spectrum and collecting initial vibration amplitude and frequency spectrum characteristics through an acceleration sensor;

[0009] S3 Subsection mileage endurance simulation: transferring the driving shaft assembly to a road spectrum test machine and simulating driving endurance according to a preset mileage;

[0010] S4 Subsection vibration retest: returning the driving shaft assembly to the NVH test machine after completing a section of preset mileage endurance, and retesting the vibration amplitude and frequency spectrum characteristics under the same time domain load spectrum;

[0011] S5 Grease performance analysis: analyzing the grease state based on the changes of the vibration amplitude and frequency spectrum characteristics.

[0012] By adopting the technical scheme, the test period is greatly shortened by combining segment simulation durability with vibration retest, the time-consuming problem of traditional road test is avoided, the test efficiency is greatly improved, and the test cost is reduced; the life of the oil is judged based on the vibration amplitude and the spectrum characteristics, the objective quantitative evaluation of the wear state is realized, and the life evaluation of the oil is more objective; the bench test is based on the real vehicle load spectrum to restore the real working condition, the load is accurately loaded by combining the NVH test machine, and the vibration data reliability is ensured, and the test conclusion is more accurate.

[0013] Optionally, in S1, a data acquisition device is arranged on the vehicle drive shaft to acquire working condition data of the drive shaft during vehicle driving; the acquisition device includes a wireless torque sensor and a speed sensor, and the working condition data includes torque and speed data.

[0014] Optionally, the wireless torque sensor is arranged on the core shaft of the drive shaft, and the speed sensor is arranged in the inner or outer wheel rod part of the left or right shaft long handle.

[0015] Optionally, in S2, a three-way acceleration sensor is arranged on the outer ring of the hub bearing to acquire vibration data.

[0016] By adopting the technical scheme, the bearing friction vibration caused by oil deterioration can be directly captured by arranging the sensor on the bearing seat, the wear sensitive area is directly monitored, and the detection accuracy is improved.

[0017] Optionally, in S3, 5000km durability is simulated first, and then S4 retest is performed after completion; continue to simulate driving to accumulate 10000km durability, and perform S4 retest again.

[0018] Optionally, the drive shaft assemblies of two different oils are installed synchronously in the same test environment, and S2-S4 are executed in parallel, wherein the same NVH test machine is used to test the vibration data; the vibration data of the two oils at the same mileage node is compared, and the oil with lower vibration amplitude or smaller selected frequency band RMS value has better performance.

[0019] By adopting the technical scheme, the comparison of the two oils is converted into a single variable experiment, the performance of the two oils is quantitatively compared, and the life of the oil is accurately judged.

[0020] Optionally, the data collected by the three-way acceleration sensor is post-processed and exported as a vibration acceleration spectrum diagram, and the vibration acceleration spectrum diagrams are compared in the selected frequency range, and the oil with smaller vibration acceleration spectrum diagram amplitude has better performance.

[0021] By adopting the technical scheme, the amplitude reflects the abnormality of the bearing as a whole, the amplitude is lower, the oil film has strong maintaining ability, and the impact between the internal parts of the bearing is fully absorbed.

[0022] Optionally, in S5, compared with the initial and each endurance stage of the vibration data, when the vibration average amplitude or RMS value increases more than the set threshold, it is determined that the grease fails.

[0023] By adopting the technical scheme, the vibration threshold is set to determine the grease failure, and precise quantitative diagnosis of the wear life is realized. The essence of grease failure is that the lubricating film is broken to cause the impact energy of the friction pair to rise.

[0024] In a second aspect, the NVH test machine provided by the application adopts the following technical scheme:

[0025] The NVH test machine comprises a base, a first driving device connected to the base, and a second driving device, the first driving device comprises a first servo motor, the second driving device comprises a second servo motor, a hub unit of a driving shaft assembly is connected with a main shaft of the first servo motor through a connecting tool, the other end of the driving shaft assembly is connected with a main shaft of the second servo motor, the first servo motor and the second servo motor drive the driving shaft assembly to rotate, and the first driving device is fixedly connected with a support, and the support is connected with an outer ring of a bearing of the driving shaft assembly.

[0026] By adopting the technical scheme, the double-servo motor closed-loop structure design of the NVH test machine makes the driving shaft core bearing bear a real torsional load, and the boundary conditions of the real vehicle load are accurately restored and the driving shaft system vibration mode is actively excited, so that high-sensitivity monitoring of the grease wear state is realized.

[0027] Optionally, the connecting tool comprises a first tool assembly, a second tool assembly and a connecting frame, the first tool assembly is fixedly connected with the hub unit, the first tool assembly is fixedly connected with the second tool assembly, the second tool assembly is connected with the connecting frame, and the other end of the connecting frame is fixedly connected with the main shaft of the second servo motor.

[0028] To sum up, the application has at least one of the following beneficial technical effects:

[0029] 1. By combining the segmented simulation durability with vibration retesting, the test cycle is greatly shortened, the time-consuming problem of traditional road testing is avoided, the efficiency of the test is improved, and the test cost is reduced;

[0030] 2. The grease failure is determined based on the threshold of the vibration amplitude and the frequency spectrum characteristics (such as the RMS value), and the objective quantitative evaluation of the wear state is realized;

[0031] 3. The real vehicle load spectrum is restored in the bench test, and the special NVH test machine is combined to ensure the accurate loading of the load and the reliability of the vibration data. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is the 100 km acceleration frequency spectrum graph in the embodiment 2 of the application;

[0033] Figure 2 is a 300 km acceleration spectrum diagram in embodiment 2 of the present application;

[0034] Figure 3 is a structural schematic diagram of embodiment 3 of the present application;

[0035] Figure 4 is a structural schematic diagram of embodiment 3 of the present application for showing a tooling assembly.

[0036] In the figure, 1, three-axis acceleration sensor; 2, hub unit; 3, first tooling assembly; 4, second tooling assembly; 5, rubber pad; 6, bracket; 7, first driving device; 8, second driving device; 9, connecting frame; 10, base. DETAILED DESCRIPTION

[0037] The following will be described in detail in combination with the accompanying drawings. Figure 1 - the accompanying drawings Figure 4 The present application will be further described in detail.

[0038] Embodiment 1: Test method for grease wear life of driving shaft, comprising the following steps:

[0039] S1 Road load spectrum generation:

[0040] A data acquisition device is arranged on the driving shaft of the test vehicle, specifically, the data acquisition device comprises a wireless torque sensor and a rotation speed sensor. The wireless torque sensor is arranged on the core shaft of the driving shaft, and is used for accurately acquiring torque data borne by the driving shaft during driving. The rotation speed sensor is arranged on the inner and outer wheel rods of the left or right shaft long handle, and is used for acquiring the rotation speed of the driving shaft.

[0041] The test vehicle is arranged to drive on the road for a certain mileage, and the data acquisition device continuously acquires the working condition data of the driving shaft during driving of the vehicle, including torque and rotation speed data. The acquired real vehicle driving working condition data is processed, and the data is converted into a time domain load spectrum that can be loaded by the NVH tester.

[0042] S2 Initial vibration benchmark test:

[0043] The driving shaft assembly to be tested is installed on the NVH tester through the hub bearing connection tooling, and a three-axis acceleration sensor 1 is installed on the bearing outer ring of the driving shaft assembly, which is used for acquiring vibration data. Arranging the sensor on the bearing outer ring can directly capture the bearing friction vibration caused by grease deterioration, directly monitor the wear sensitive area, and improve the detection accuracy.

[0044] Start the NVH test machine and load the drive shaft assembly according to the time-domain load spectrum generated above to simulate the load condition during actual vehicle driving. During the loading process, the three-axis acceleration sensor 1 collects the initial vibration amplitude and frequency spectrum characteristic data of the drive shaft assembly in real time and transmits the data to the data acquisition system for storage.

[0045] The collected vibration data is processed, including filtering, denoising, frequency spectrum analysis and other operations, to generate an initial vibration acceleration frequency spectrum graph, providing basic data for subsequent grease performance analysis.

[0046] S3 Subsection Mileage Durability Simulation:

[0047] The drive shaft assembly that has completed the initial vibration benchmark test is disassembled from the NVH test machine and transferred to the road spectrum test machine. According to the installation requirements of the road spectrum test machine, the drive shaft assembly is correctly installed and fixed to ensure its stable operation during the test.

[0048] For example, first simulate driving for 5000 kilometers of durability, and on the road spectrum test machine, simulate the driving process of the vehicle according to the preset program and parameters, so that the drive shaft assembly bears the corresponding load and fatigue. After completing the 5000 kilometer durability simulation, the test is paused, the drive shaft assembly is disassembled, and preparation is made for subsection vibration retesting (refer to step S4). Then, continue to simulate driving to a cumulative 10000 kilometer durability, and again pause the test for the next subsection vibration retesting (refer to step S4).

[0049] S4 Subsection Vibration Re-Testing:

[0050] After completing a predetermined section of durability, the drive shaft assembly is returned to the NVH test machine, and the drive shaft assembly is reinstalled on the NVH test machine according to the installation method in the initial vibration benchmark test, and the three-axis acceleration sensor 1 is connected. Then, the drive shaft assembly is loaded according to the same time-domain load spectrum to simulate the load condition during actual vehicle driving.

[0051] During the loading process, the three-axis acceleration sensor 1 collects vibration amplitude and frequency spectrum characteristic data of the drive shaft assembly again, and transmits the data to the data acquisition system for storage. The collection frequency and data processing method are the same as those in the initial vibration benchmark test, and a subsection vibration acceleration frequency spectrum graph is generated for comparison and analysis with the initial vibration data.

[0052] S5 Grease Performance Analysis:

[0053] The initial vibration acceleration frequency spectrum is compared with the vibration acceleration frequency spectrum of each durability stage to analyze the change of vibration amplitude and frequency spectrum characteristics. The vibration data of the initial and each durability stage are compared, the frequency interval is selected, and the vibration average amplitude or RMS value is obtained by processing the data. The vibration average amplitude or RMS value obtained by the segmented vibration retest is compared with the vibration average amplitude or RMS value obtained by the initial vibration reference test. When the vibration average amplitude or RMS value increases by more than a set threshold, the grease failure is determined. The set threshold determines the grease failure, and the precise quantitative diagnosis of the wear life is realized. The essence of grease failure is that the rupture of the lubricating film leads to the increase of the impact energy of the friction pair.

[0054] Example 2: Test method of driving shaft grease wear life, which is different from example 1 in that two different greases of the driving shaft assembly to be tested are installed in the same test environment to perform S2-S4 experiments, and then the vibration data are compared to determine which grease has better performance, thereby comparing the life of the two greases. The specific situation is as follows:

[0055] S2 Initial vibration reference test:

[0056] Two driving shaft assemblies of the same batch number are selected, and the two driving shaft assemblies are filled with different greases. In order to further reduce the influence of the differences in the driving shaft assembly itself on the test results, multiple driving shaft assemblies of the same batch number can be selected, and then the random driving shaft assemblies are filled with different greases, and the driving shaft assemblies are divided into two groups according to the different greases filled.

[0057] All driving shaft assemblies to be tested are tested in turn using the same NVH tester. Start the NVH tester, load the driving shaft assembly according to the time domain load spectrum, and simulate the load working condition of the actual vehicle driving. In the loading process, the three-axis acceleration sensor 1 collects the initial vibration amplitude and frequency spectrum characteristic data of the driving shaft assembly in real time, and transmits the data to the data acquisition system for storage.

[0058] The collected vibration data are processed, including filtering, denoising, frequency spectrum analysis and other operations, to generate the initial vibration acceleration frequency spectrum, which provides basic data for subsequent grease performance analysis.

[0059] S3 Segment mileage durability simulation:

[0060] The driving shaft assembly that has completed the initial vibration reference test is disassembled from the NVH tester and is installed on the road spectrum tester for segment durability simulation.

[0061] For example, first simulate 5000 km durability, simulate the driving process of the vehicle on the road test machine according to the preset program and parameters, and it is worth noting that the preset program and parameters of all road test machines should be the same. After completing the 5000 km durability simulation, the test is suspended, the drive shaft assembly is disassembled, and the segmented vibration retest is prepared. Then, continue to simulate driving to 10000 km durability, suspend the test again, and perform the next segmented vibration retest. Other mileage can also be selected for segmented testing, and 100 km and 300 km are used in this embodiment.

[0062] S4 segmented vibration retest:

[0063] After completing a predetermined mileage durability, all drive shaft assemblies are disassembled, and the drive shaft assemblies are returned to the NVH test machine one by one, and the three-axis acceleration sensor 1 is connected. Then, load the drive shaft assembly according to the same time domain load spectrum to simulate the load condition when the vehicle is driving.

[0064] During the loading process, the three-axis acceleration sensor 1 again collects the vibration amplitude and frequency spectrum characteristic data of the drive shaft assembly, and transmits the data to the data acquisition system for storage. The collection frequency and data processing method are the same as the initial vibration benchmark test, and the segmented vibration acceleration frequency spectrum is generated for comparison and analysis with the initial vibration data.

[0065] S5 oil performance analysis:

[0066] Compare the vibration data of the two kinds of oils at the same mileage node, and compare and analyze with the initial vibration data, refer to Figure 1 and Figure 2 . Figure 1 The acceleration frequency spectrum obtained by retesting after 100 km durability simulation of the two kinds of oils, Figure 2 The acceleration frequency spectrum obtained by retesting after 300 km durability simulation of the two kinds of oils. By comparing the amplitude of the curve in the 500-1000 Hz interval, the first kind of oil has lower vibration amplitude in all directions and better damping performance.

[0067] According to the vibration amplitude or the size of the selected frequency band RMS value, the performance of the oil is judged. The one with lower vibration amplitude or smaller selected frequency band RMS value has better oil performance. In this way, the comparison of the two kinds of oils is converted into a single variable experiment, the performance of the two kinds of oils is quantitatively compared, and the life of the oil can be accurately judged.

[0068] Embodiment 3: The NVH test machine is applied in embodiment 1 or embodiment 2, which includes a base 10, a first driving device 7 and a second driving device 8 connected to the base 10. The first driving device 7 and the second driving device 8 can move axially relative to the base 10 to adapt to drive shaft assemblies of different lengths.

[0069] The first driving device 7 comprises a first servo motor, and the second driving device 8 comprises a second servo motor. The hub unit 2 of the driving shaft assembly is connected with the main shaft of the first servo motor through a connecting tool, for simulating the resistance of the wheel to the hub unit 2 of the driving shaft assembly in the vehicle travel. The other end of the driving shaft assembly is connected with the main shaft of the second servo motor, for simulating the driving of the driving shaft assembly by the vehicle power source (automobile motor).

[0070] The first driving device 7 is fixedly connected with a support 6, and the bearing outer ring of the driving shaft assembly is connected with the support 6, which can be fixedly connected or abutted. The support 6 is used to limit the rotation of the bearing outer ring. In order to reduce the influence of the vibration of the NVH test machine itself in the running process on the detection data, a rubber pad 5 is arranged between the support 6 and the bearing outer ring.

[0071] The connecting tool comprises a first tool assembly 3, a second tool assembly 4 and a connecting frame 9. The first tool assembly 3 is a flange plate, one end of which is fixedly connected to the hub unit 2, and the other end is fixedly connected to the second tool assembly 4. One end of the second tool assembly 4 is disc-shaped and is fixedly connected to the flange plate through bolts, and the other end is hexagonal, which is used to be inserted into the connecting frame 9 to realize circumferential fixation to transmit torque. The connection mode of the second tool assembly 4 and the connecting frame 9 can also adopt other connection structures, such as spline connection. The connecting frame 9 is connected with the main shaft of the first servo motor, and the first servo motor drives the hub unit 2 to rotate through the connecting frame 9, the second tool assembly 4 and the first tool assembly 3.

[0072] The embodiments of the specific embodiment are the preferred embodiments of the present application, and are not limited to the protection scope of the present application, wherein the same parts are indicated by the same reference numerals. Therefore, any equivalent changes made according to the structure, shape and principle of the present application should be covered within the protection scope of the present application.

Claims

1. Test method for grease wear life of a drive shaft, characterized in that Comprising the following steps: S1 Road load spectrum generation: Collecting driving shaft working condition data in actual vehicle driving and converting into time domain load spectrum that can be loaded on a bench tester; S2 Initial vibration benchmark test: Installing the driving shaft assembly to be tested on an NVH tester through a hub bearing connecting tool; loading the time domain load spectrum and collecting initial vibration amplitude and frequency spectrum characteristics through an acceleration sensor; S3 Sectional mileage durability simulation: Transferring the driving shaft assembly to a road spectrum tester and simulating driving durability according to a preset mileage section; S4 Sectional vibration retest: Returning the driving shaft assembly to the NVH tester after completing a preset mileage durability section and retesting the vibration amplitude and frequency spectrum characteristics under the same time domain load spectrum; S5 Oil and grease performance analysis: Analyzing the oil and grease state based on the changes in the vibration amplitude and frequency spectrum characteristics.

2. The test method for drive shaft grease wear life according to claim 1, characterized in that, In S1: A data collection device is arranged on the vehicle driving shaft for collecting driving shaft working condition data in vehicle driving; the collection device comprises a wireless torque sensor and a rotational speed sensor, and the working condition data comprises torque and rotational speed data. The wireless torque sensor is arranged on the core shaft of the driving shaft; and the rotational speed sensor is arranged in the inner or outer wheel rod of the left or right shaft long handle.

3. The method of claim 2, wherein the method further comprises: In S2, a three-way acceleration sensor (1) is arranged on the outer ring of the hub bearing for collecting vibration data.

4. The method of claim 1, wherein In S3, 5000 km of driving durability is simulated first, S4 retest is performed after completion, and 10000 km of driving durability is simulated, and S4 retest is performed again.

5. The method of claim 1, wherein The driving shaft assemblies of two different oils are synchronously installed in the same test environment, S2-S4 are performed in parallel, and the same NVH tester is used to test the vibration data; the vibration data of the two oils at the same mileage node are compared, and the oil with lower vibration amplitude or smaller selected frequency band RMS value has better performance.

6. The method of claim 1, wherein The data collected by the three-way acceleration sensor (1) is post-processed and exported as a vibration acceleration spectrum diagram, which is compared in a selected frequency range, and the oil with smaller vibration acceleration spectrum diagram amplitude has better performance.

7. The method of claim 6, wherein the method further comprises: In S5, the initial and each durability stage vibration data are compared, and when the vibration average amplitude or RMS value increases by more than a set threshold, the oil is determined to be invalid.

8. The method of claim 1, wherein, The driving shaft assembly comprises a base (10), a first driving device (7) and a second driving device (8) connected to the base (10), the first driving device (7) comprises a first servo motor, the second driving device (8) comprises a second servo motor, a hub unit (2) of the driving shaft assembly is connected with a main shaft of the first servo motor through a connecting tool, the other end of the driving shaft assembly is connected with a main shaft of the second servo motor, the first servo motor and the second servo motor drive the driving shaft assembly to rotate, the first driving device (7) is fixedly connected with a support (6), and the support (6) is connected with a bearing outer ring of the driving shaft assembly.

9. The NVH tester as defined in claim 1, wherein, ​ 10. The NVH tester of claim 9, wherein, The connecting tool comprises a first tool assembly (3), a second tool assembly (4) and a connecting frame (9), the first tool assembly (3) is fixedly connected with the hub unit (2), the first tool assembly (3) is fixedly connected with the second tool assembly (4), the second tool assembly (4) is connected with the connecting frame (9), and the other end of the connecting frame (9) is fixedly connected with the main shaft of the second servo motor.

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