Analysis of the cause of whistling of gear transmission system assembly
The meshing transmission error of the gear is mainly to be controlled within the entire operating load range through micro-modification when the control system is deformed, and the transmission error is at a low level. The micro modification of gear pair mainly includes tooth profile modification and tooth direction modification. Tooth profile modification refers to removing a part of the material from the tooth tip or tooth root of the gear tooth to reduce the elastic deformation and machining error of the gear teeth during the gear meshing process. The impact phenomenon caused by meshing in and meshing out; tooth modification is suitable for poor gear support rigidity, serious gear meshing eccentric load, compensation for gear meshing skew caused by random errors such as manufacturing and installation, and can compensate for various elastic deformations. gear tooth eccentric load phenomenon.
Experience has proved that the correctly calculated micro-modification parameters can effectively reduce the transmission error of the gear pair; reducing the transmission error of the gear pair can effectively reduce the vibration response amplitude of the system to achieve the purpose of improving the NVH of the system. The system coupling mode is affected by the suspension of the whole vehicle. The influence of the rigidity of the assembly and the stiffness of the assembly shell needs to be analyzed by the method of calculating the mass matrix and the stiffness matrix of the assembly. Due to the complex calculation formula, the finite element software is usually used for calculation.
Order Noise Analysis of Gear Transmission System Assembly
1 Question input
During the vehicle-mounted NVH test, the near-field noise data can be collected through the LMS data acquisition front-end (since the vehicle has noise reduction packages, the simulation technology is difficult to achieve, so the near-field noise is used as the analysis basis), and the collected data is passed through The LMS Test.Lab data analysis software analyzes the noise order of the near-field noise, and finds out the corresponding order of howling. Then through the order analysis of the howling noise, the excitation source of the howling noise is determined.
In this paper, the test data of the company’s electric drive assembly vehicle equipped with NVH test customer feedback is shown in Figure 1.
Figure 1 Comparison of near-field noise between a certain type of drive assembly and the model used by customers (17th order)
According to feedback from a domestic customer, under the WOT working condition of the whole vehicle, the whistle score of the plant-tooth scheme is 5.5 points, and the customer’s original scheme is rated as 6 points. optimization), the 5.38th order of the secondary gear noise is better than the original scheme (without optimization).
Establishment of Analytical Model of MASTA Reducer
The MASTA analysis model established according to the electric drive assembly product is shown in the following figure:
Figure 2 MASTA analysis model of an electric drive assembly
The gear parameters of the electric drive assembly are shown in the following table:
|Basic parameters||high speed pinion||high speed gear||low speed pinion||low speed gear|
|number of teeth||17||60||19||60|
|Tooth width (mm)||41||38||51||45|
|Normal pressure angle (°)||20||20||20||20|
|Center distance (mm)||88||88||135||135|
MASTA software analysis results
After entering the macro parameters and micro modification of the gear pair in the software, through MASTA software simulation, the transmission error of the high-speed gear pair of the electric drive assembly under the WOT condition of the whole vehicle is obtained as shown in Figure 3. The high-speed gear pair is shown in Figure 3. The Fourier transform result of the transfer error is shown in Figure 4. It can be seen from the figure that under the WOT condition of the whole vehicle, the peak-to-peak calculation result of the transmission error of the high-speed gear pair meets the design requirements. The cause of the problem should be the presence of system resonance.
Fig. 3 Transmission error of high-speed gear pair (peak-to-peak value: 0.4311μm)
Fig. 4 Fourier transform of transmission error of high-speed gear pair (amplitude: 0.085μm)
Using the NVH analysis module of the MASTA transmission analysis software, input the microscopic modification parameters of the gear, and the corresponding analysis results of the casing (system response vibration acceleration) are compared with the measured results as shown in Figure 5. From Figure 5, the test results and the analysis results are compared From the trend of the curve, there is a large deviation between the test results and the analysis results after the motor speed reaches 6000rpm. Before 6000rpm, the analysis results match the test results relatively well, especially at the speed point where the order noise peaks. The peak point can find the corresponding system response peak point.
Through the speed-frequency conversion formula:
In the formula,
F is the assembly response frequency (Hz);
k is the fundamental frequency multiplier (basic frequency k=1);
n is the motor speed, that is, the transmission input shaft speed;
z1 is the number of teeth of the high-speed drive gear;
z2 is the number of teeth of the high-speed driven gear;
z3 is the number of teeth of the low-speed drive gear;
When the motor speed is calculated by formula (1) between 6000-9000rpm, the system coupling frequency corresponding to the 17th order is between 1700-2550Hz, and the system coupling mode in this frequency range is analyzed by software, and the coupling mode order is in Between the 24th and 33rd orders as shown in Figure 6, through the modal analysis results of the analysis software, within this coupling modal order range, the peak vibration acceleration of the assembly appears on the assembly motor shell as shown in Figure 7, However, due to customer reasons, we cannot obtain the internal model of the motor, and the motor analysis model is inaccurate, resulting in inaccurate analysis results after 6000rpm. Therefore, the 17th-order noise after the motor speed exceeds 6000rpm, and the 34th-order noise after the motor speed exceeds 3000rpm, vibration The results of the analysis are not discussed.
Therefore, the results of this analysis can be used as a sample for NVH evaluation of this electric drive assembly.
Figure 5 Comparison of test results (green line) with vibration analysis results
Figure 6 System coupled modal results
4 Experimental verification analysis results
Since the client proposed that he did not want to change the shape of the mount and the casing, he only wanted to solve the problem by adjusting the microscopic modification of the gear pair. Therefore, the members of the project research team only fine-tuned the microscopic parameters of the gear. , After the adjustment of the micro-modification parameters of the high-speed gear pair, the calculation results of the 17th-order vibration response sound power of the casing of the assembly are compared as shown in Figure 8 and Figure 9, and the calculation results of the 34th-order vibration response sound power of the casing of the assembly As shown in Figure 10 and Figure 11, it can be seen from the analysis and comparison results that the peak noise power of the 17th and 34th orders both decreased by about 3 times, and the order noise trend did not change much.
Figure 8 The 17th-order response sound power of the improved front assembly
Figure 9 The 17th-order response sound power of the assembly after improvement
Figure 10 The 34th-order response sound power of the front assembly is improved
Figure 11 The 34th-order response sound power of the assembly after improvement
Gear transmission system assembly loading test
In order to verify the correctness of the above-mentioned product optimization results and software analysis results, the optimized assembly product is tested for loading, and the test results are compared with the test results before optimization. Under the WOT condition of the whole vehicle, the test effect of the optimized reducer loading noise test is better than that before optimization. The near-field noise data is collected through the customer’s LMS data acquisition front-end, and the collected data is subjected to noise order analysis of the near-field noise through the LMS Test.Lab data analysis software to verify the loading results. The test results are as follows:
Figure 12 Near-field noise curve 17th order
Figure 13 Near-field noise graph 34th order
For the convenience of comparison, the 17th-order noise test data before and after optimization are shown in Figure 12. Among them, the red curve is the 17th-order interior noise order slice diagram of the reducer assembly before optimization, and the green is the 17th-order noise order slice diagram after optimization (inspect within 6000rpm).
The 34-order noise test data before and after optimization are shown in Figure 13. Among them, the red curve is the slice diagram of the 34th-order interior noise order of the reducer assembly before optimization, and the green is the optimized 34th-order noise order slice diagram (within 3000rpm).
From Figure 12 and Figure 13, it can be seen that the 17th-order noise has a significant decrease trend within 6000rpm, but individual speed ranges have increased, and the near-field noise trend is roughly the same. It is not obvious, which verifies the correctness of this analysis. After 3000rpm, the improvement is obvious, which is related to the inaccuracy of the motor model, so no relevant analysis is made here.
01、The high-speed and highly integrated electric drive transmission system of pure electric vehicles changes the coupling mode of the system due to the high degree of integration, which makes the NVH problem of the electric drive assembly more complicated;
02、Reducing the transmission error of the gear pair can reduce the order noise value as a whole, but cannot change the trend of the order noise;
03、The noise of the high-speed and highly integrated electric drive transmission system of pure electric vehicles is greatly affected by the mode of the assembly system. To change the whistling problem in a certain speed range, that is, to change the trend of the order noise, it is necessary to optimize the mode of the assembly shell and the suspension of the assembly. set stiffness;
04、From the analysis results of the noise reduction of the high-speed and highly integrated electric drive transmission system of pure electric vehicles, the noise reduction of the gear transmission system alone cannot effectively solve the whistling problem, and it is necessary to start from the stiffness of the entire integrated powertrain.
Editor: Huang Fei