A point-contact conjugate hourglass worm drive based on the meshing theory of conjugate tooth surfaces generated by two generating surfaces

Abstract

To solve the problems of narrow contact area and small contact ratio of the involute cylindrical worm helical gear drive, this paper proposed a point-contact conjugate hourglass worm drive (PCHW drive) based on the meshing theory of conjugate tooth surfaces generated by two generating surfaces. The hourglass worm and worm gear are generated by the helix surface of an involute helical gear and that of an involute cylindrical worm. A mathematical model of the drive is established and a method for solving contact points based on involute pitch point is given. The instantaneous transmission ratio is proved theoretically to be constant and transmission error is zero. The formation mechanism of the conjugate surfaces of the drive is revealed. The results of the tooth contact analysis for a numerical example show that he contact area of this drive is wider, the contact ratio is slightly increased compared to the involute cylindrical worm helical gear drive. Furthermore, the drive is insensitive to manufacturing and assembly errors. A prototype is manufactured and meshing test is performed to verify the theoretical correctness.