Abstract: From the point of view of the contact line and the meshing limit line, the contact performance of double enveloping TI (Torioidal Involute) worm gearing is analysed. The results show that only when there is one meshing limit line on the worm tooth flank or two lines which are not coincide with each other can the second contact line be seen on the worm tooth flank of double enveloping TI worm gearing. Within the range of machining, if the helix angle adopts a bigger value, it may improve the meshing performance and develop the advantages of double enveloping TI worm gearing. The studies are practicably instructive for selecting reasonable design parameters.

Key words: Double enveloping TI worm gearing, Meshing limit line, Second contact line, Tooth flank contact analysis