Helical gear squeal is a kind of pure noise with medium high rate and low sound pressure level, which is caused by the load on the meshing gear pair and changes with the speed of the gearbox. Taking the helical gear reducer of the first class electric vehicle shown in the figure as an example, the gear teeth of the two helical gears are regarded as springs, the wheel body is regarded as mass, and the whole is regarded as a spring mass vibration system. In the process of gear transmission, due to the existence of clearance, the pitch line impact force and meshing impact force will be caused, which will result in gear vibration, which will be transmitted to the housing through the shaft, bearing, and bearing seat, causing shell wall vibration, and finally radiating into the air to form noise. Many studies have shown that the squealing noise of helical gears is not only related to the internal excitation, namely, meshing impact excitation, stiffness excitation, error excitation, but also affected by the micro design of gears.
The whistling frequency f can be calculated by the formula:
Where:
N is the rotational speed of the helical gear box;
Z is the meshing order of the helical gear pair, that is, the number of teeth engaged in the meshing when the driving wheel rotates for one cycle.