Tertiary negative-deviation flexing contact type gear drive of non- profile-shifted tooth profile

摘要

In a cup-shaped flexing contact gear (1), both a rigid internal gear (2) and a flexible external gear (3) are made to be non- profile-shifted spur gears, an opening (3a) of the flexible external gear (3) is set in a state of negative deviation wherein a deflection of the opening is lower in value than a normal deflection; a moving locus is obtained through rack approximation of teeth of the external gear to the internal gear at respective sections of rotation of tooth trace of the flexible external gear (3), an envelope (e) is obtained by overlapping the moving locus on one of sections of rotation, another moving locus is obtained in a section of rotation at the end portion of tooth trace on the side of a diaphragm or in the vicinity of the outside of the end portion and is smoothly connected to the envelope to thereby obtain a composite curve (L) . A curve (FE) is obtained by similarity transforming at a reduction ratio of 1/2 a portion from a starting point (A) of the envelope (e) to a terminating point (E) thereof corresponding to two times the working depth in the direction of the depth from an apex of a moving locus (l o) when deviation is 0, using the terminating point as an original point, and this curve is made to be each of main portions of convex tooth profiles at tooth faces of the both gears (2, 3). Further, a composite curve (MFE) including a straight line (MF) having a limited pressure angle (&agr;.sub.M) associated with a deflection value of the opening inserted in the vicinity of a datum point (M) of tooth profile and a transient curve smoothly connecting the straight line to the main portion of the convex tooth profile is made to be each of tooth profiles at the tooth faces of the both gears.