In the picture:
RR — pitch circle radius;
RRB — radius of base circle;
RRF — root circle radius;
φ — half tooth angle of tooth root.
Bending stiffness Kb:
Shear stiffness KS:
The axial compression stiffness Ka is as follows
When the first pair of teeth on the internal gear mesh:
When the second pair of teeth on the internal gear mesh:
For the internal meshing pair, the stiffness calculation equation of the outer gear meshing with the internal gear is the same as that of the outer gear of the outer gear meshing pair of the external gear. The formula can be referred to. It is only different in the integral region. It is assumed that the outer gear is the driving wheel.
When the first pair of teeth on the outer gear mesh:
When the second pair of teeth on the outer gear mesh: