Pressure nephogram during helical gear meshing:

It can be seen from figures 1 to 4 that when two helical gears mesh, they can be summarized into two modes, which are carried out circularly, that is, the meshing form of single tooth pair and double tooth pair. The two forms are carried out in turn. During the whole meshing process of the driving wheel, the force on the tooth root gradually increases. At this time, the meshing point gradually moves upward. Obviously, when the helical gear exits the meshing process, the force on the tooth root is 0n. In this process, there is always the alternation of single and double tooth pairs, resulting in the unstable force on the helical gear, which is very easy to cause vibration and machine noise. In the above figure, it can be explained that the state with small contact stress is when the double tooth pair is engaged, so the meshing stress of the single tooth pair is large, and the contact stress value will change significantly at the moment of switching between the two states. This is because the load distribution between two tooth pairs changes due to the change of helical gear meshing state. The load is mainly concentrated on the middle helical gear, so the stress at the helical gear meshing increases gradually. With the progress of the helical gear meshing process, when a pair of teeth gradually withdraw from meshing, the state at this time is what we call the single pair meshing state. Its stressed helical gear has only the intermediate gear, so its stress is large. As time goes on, the next pair of helical gears slowly mesh in, forming a double pair state. The stress is equally distributed by the two pairs of helical gears, Therefore, the stress of a single helical gear decreases. In their critical state, that is, the time point when the single and double helical gears change, there is a sudden change in stress, which is interpreted as stress fluctuation. This condition is unfavorable to the helical gear and affects the service life of the helical gear.