Circular Spline

The rigid, internally toothed outer ring of a harmonic drive, usually the fixed part.

A harmonic drive has three parts: an elliptical wave generator, a thin-walled, flexible flexspline (with external teeth), and a circular spline (with internal teeth). The circular spline is a thick internal-tooth ring, usually with 2 more teeth than the flexspline. As the wave generator rotates, it flexes the flexspline into an ellipse, and the teeth at the two ends of the ellipse's long axis mesh with the circular spline; that meshing point rotates along with the wave generator. For each full turn of the wave generator, the flexspline shifts relative to the circular spline by only as many teeth as the tooth-count difference between them, which is how the mechanism achieves a large reduction ratio. The common configuration fixes the circular spline to the housing and takes output from the flexspline. The circular spline's tooth-form accuracy and stiffness directly affect backlash and transmission accuracy.

ExampleWith a 200-tooth flexspline and a 202-tooth circular spline, fixing the circular spline and taking output from the flexspline gives a reduction ratio of 200 ÷ 2 = 100:1.

Also called

Rigid Spline

Related

Strain Wave Gear (Harmonic Drive) · Flexspline · Wave Generator · Gear Ratio · Backlash · Leaderdrive

Sources

Strain wave gearing - Wikipedia