Mechanism of gear surface corrugation order noise

In the gear vibration and noise phenomena of the automobile industry, gear screeching and knocking are usually the most common ones.Gear squealing noise generally refers to the order directly related to the number of teeth of the active gear, including the basic order and its resonance order.In gear resonance order, besides integer multiple order of tooth number, there is also fractional multiple order of active tooth number, which is usually called ghost step in industry.

Whether integral or fractional times of gear order, it can be universally understood as the resonance order of gear meshing vibration.This paper mainly focuses on the characteristics of gear surface corrugation order noise, analyses and discusses its excitation mechanism, puts forward the optimization improvement direction of this kind of noise, and verifies it by an actual case of tooth surface corrugation noise improvement.

The main conclusions are as follows:

1) When the tooth surface corrugation is more pronounced than other exciting sources of gear pair, such as the arithmetic average height Wa of the crest and valley of the tooth surface corrugation reaches 20 um, the corrugation squeal order noise will occur. The order value is equal to the total number of corrugation peaks and valleys of each tooth surface after one revolution of the drive gear.The order value formed by the tooth surface corrugation, the total number of peak and trough on each tooth surface and the number of peak and trough of local bifurcation of the tooth surface contact transfer error curve are identical in value.

2) Measures to solve the order noise caused by gear corrugation are mainly to reduce the amplitude of gear corrugation below that of other exciting sources so that it can not be the main exciting source of gear vice-outstanding. For example, it is better to improve the arithmetic average height Wa of gear corrugation crest and trough below 10 um in this paper.

3) Surface geometric structure excitation of friction pair of continuous rotary gear can be seen as Fourier series consisting of continuous integrable function r(t) and corresponding expanding infinite order every revolution period. The ghost order formed by tooth surface corrugation always has a fixed proportional relationship with the number of teeth of the driving gear, and in general it is a fractional proportional relationship.If there is a transmission in this paper, the fourth, fifth and sixth gears have a ratio of 3.77 to the main reducing order.

4) According to the value of “ghost step” of gear surface corrugation, there is always a fixed proportion relationship with the number of teeth of the driving gear, which can provide a quick and effective direction or basis for investigating noise problems of Engineering order. Of course, the cause of “ghost step” is also the case of other excitation types of gear pairs.

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