The sliding coefficient is an important parameter to measure the relative sliding degree between the tooth surfaces of the meshing gear pair. Since sliding will cause the surface of the gear teeth to be glued and even worn, resulting in serious consequences, it is necessary to study the sliding coefficient of the helical gear, so as to improve its anti-glued and anti-wear ability.
Generally, when the sliding coefficient is at (- 1, 1), the gear mesh is perfect, when it is at (- 3, 3), the gear mesh is good, and when it is at (- ∞, – 3) and (3,+∞), the gear mesh is poor. As shown in the figure, the slip coefficient curves of the helical gear pair 0 # unmodified, 1 # optimized and 9 # optimized are all between (- 0.95, 0.49), and the meshing performance is perfect, but the optimized modification does not cause the change of the gear slip coefficient, so it can be considered that the above optimized modification method has little effect on the slip degree between the teeth of the helical gear pair. In addition, it can be found from the figure that the sliding coefficient of large and small gears is close (red line and green line), so that the relatively balanced gear sliding rate can make the wear degree of the two helical gears consistent in the transmission process, thus improving the utilization ratio of the helical gears.
| Original scheme | Option 1 | Option 2 | |
| Number of teeth Z1 | 30 | 32 | 34 |
| Number of teeth Z2 | 51 | 49 | 47 |
| Sliding coefficient ζ1 | （-0.95，0.49） | （-0.89，0.49） | （-0.84，0.49） |
| Sliding coefficient ζ2 | （-0.94，0.49） | （-0.94，0.49） | （-0.95，0.46） |
| Number of teeth ratio | 1.7 | 1.53 | 1.38 |
Of course, if there is a higher requirement for the scuffing and wear resistance of helical gears, it can be achieved by properly adjusting the tooth number ratio of large and small gears. As shown in the table, the absolute value of the sliding coefficient can be reduced by properly reducing the tooth number ratio under the condition that the center distance and the modification coefficient remain unchanged.