Figure 1 shows the influence curve of helix angle on the time-varying meshing force of the helical gear pair at different speeds. When the helix angle changes in the range of 30 ° to 32.5 °, the time-varying meshing force of the helical gear under low speed (2000r/min), medium speed (5000r/min) and high speed (10000r/min) conditions increases with the increase of helix angle, but excessive helix angle (more than 32.5 °) will not further increase the force excitation. From Figure 1 (a), it can be found that changing the helix angle can not completely eliminate the impact of meshing in and out, but an appropriate helix angle (30 °) can make the meshing more smooth (the curve is relatively smooth), and the time-varying meshing force is significantly reduced, thereby reducing the impact of meshing in and out.
Figure 2 shows the influence curve of helix angle on the time-varying meshing stiffness of the helical gear pair. It is obvious that the larger the helix angle is, the greater the time-varying meshing stiffness is, and the stronger the vibration of the helical gear pair is.
Therefore, considering that the meshing impact excitation and stiffness excitation are both important factors affecting the transmission noise of helical gear pairs, if the dynamic excitation is reduced, the small helix angle should be selected on the premise of meeting the requirements of use and reducing the time-varying meshing force.