Experimental Investigation of the Effect of Gear Ratio on the Dynamic Behavior of a Helical Gear Pair.

When the effect of thrust force due to helix angle of helical gear is considered, the vibration behavior of a gear unit becomes complicated. Therefore, it is important to reveal the behavior of the gear vibration in all directions as well as the vibration of shafts. In this work, the vibration of helical gear units with various gear ratios under both increasing and reducing conditions has been investigated experimentally. The dynamic responses of transverse, rotational, tilting and axial vibrations of helical gears are measured by acceleration pick-ups mounted on the gear blank and modal behavior is interpreted based on a scheme involving modulation due to shaft rotation. The modes of shafts and gears are measured precisely using a laser Doppler velocimeter. The experiments were conducted by interchanging a driving gear-shaft-bearing assembly with a driven one to eliminate the effect of tooth form errors. First, the effect of helix direction and bearing fixing configuration was revealed for a gear pair with unity gear ratio. Secondly, it was demonstrated that there is little discrepancy between increasing and reducing operation except for those effect of installing configurations such as bearing fixing conditions.