# Vibration caused by natural frequency of automobile gear

All defective automobile gears will produce high-level pulses in operation, which will usually arouse the natural frequency (also known as natural frequency) of automobile gears. The test diagram of vibration amplitude spectrum caused by natural frequency is shown in the figure. Substitute N1 = 624 R / min and N2 = 128 R / min into the formula, F1 = 65.4 Hz and F2 = 12.8 Hz; Substitute formula (2) to get FC = 83 Hz.

On this spectrum, there is no engagement frequency of 83 Hz, but there is a prominent peak of 19.5 Hz, and the amplitudes of 2-fold, 3-fold and 4-fold are also large. Then, the frequency band near 12.5 Hz is analyzed by refining the spectrum. The detailed spectrum is shown in Figure 5. At this time, it is found that there is a 12.8 Hz sideband near 12.8 Hz, and 12.8 Hz is exactly the rotation frequency of the driven wheel.

In order to further find out the cause, adjust the motor speed to 426r / min, and the frequency of 19.5 Hz in the spectrum diagram is allowed to exist, which shows that 19.5 Hz is the natural frequency of the automobile gear. When the automobile is running, the strong impact of the automobile gear excites the automobile gear to vibrate at the natural frequency. According to the obtained information, there are some faults such as tooth deformation in automobile gears, and the main vibration source is on the driven wheel.

After parking and disassembling the main reducer for inspection, it is found that the surface of the driven gear teeth is uneven, and the top edge of three teeth of the driven wheel presents step protrusion due to long-term collision. When the automobile gear is running, the teeth of the driven wheel must collide with the root of the teeth of the driving wheel. It is natural for the automobile gear to arouse the natural frequency of the automobile gear. The frequency components of automobile gear vibration caused by this situation are: the side band is generated by the resonance modulation phenomenon of automobile gear natural frequency with automobile gear natural frequency and frequency doubling as the carrier frequency and the conversion frequency and higher harmonic of automobile gear as the modulation frequency.

Scroll to Top