Abstract:
This thesis presents the effects of geometrical parameters and gear tooth contact on power loss in spur and helical gears. Gear parameters that are helix angle, pressure angle and face width that their effects on power loss are still unclear are focused on this research. Experiments were done to measure power losses by using back to back gear test rig. The effects of gear tooth contact were studied by painting gear teeth before experiments. The areas that the paint was peeled off after experiment represent the actual tooth contact areas. These tooth contact patterns were used along with experimental results and gear meshing model to explain the mechanism of gear sliding loss further.From the experiments, the gears having larger helix angle have higher sliding loss. The gears having smaller pressure angles or narrower face width have higher sliding loss. The areas of tooth contact increase as load increase. The contact areas extend to almost full tooth area at the maximum applied load. By comparing the experimental results with the estimated results calculated using the former full tooth contact model, the estimated results showed the same trend with the experimental results in the case of the effects of pressure angle and face width. For the effect of helix angle, the estimated results show the maximum sliding loss at helix angle 22 degree, but from the experiments the gear having helix angle 33.5 degree has higher sliding loss. However when the data of tooth contact patterns were used in the calculation, all estimated results agree well with the experimental results. The estimated sliding loss of the gear pair having helix angle 33.5 degree is higher than that of gear having helix angle 22 degree. This is because the tooth contact areas of gear having helix angle 22 degree are narrower than the areas of gear having helix angle 33.5 degree, and at the non-contact area there are no sliding loss. These results are agree well with the experimental results. The estimated results in the other cases are also closer to the experimental results than the results estimated from the former gear model