The Basics of Strain Wave Gear
abstract:Using the elastic deformation principle, a strain wave gear can produce a high ratio gearbox that ca...
Using the elastic deformation principle, a strain wave gear can produce a high ratio gearbox that can be used in a variety of applications. It can be compact, and offers reasonable speed-to-torque conversion. It can be integrated into existing applications, and its simplicity allows it to be easily fabricated.
A strain wave gear set has three basic components: the flexspline, the elliptical wave generator, and the outer circular spline. These three parts are used to produce the desired gear ratio.
The formulas that define the characteristics of strain wave gearing were developed by analyzing the motion of teeth and extrapolating from standard engineering practice. However, they can be modified by specific experimental tests. If the results of these tests are unexpected, the formulas may be adjusted accordingly.
The tensile stress in the deflected strain gear is the determining characteristic. This stress is dependent on the number of teeth, the contact pressures, and the material of the gear. The area of contact at any point of time must be multiplied by the surface endurance limit of the gear material. It is also necessary to consider the point-loading effect.
When the radial distances are changed, the strain wave advances a large number of areas of contact. The stress at the base of the wave is slightly more than half as much as the crest. The total strain wave height is the same as the difference in radial distances.
The elliptical wave generator consists of an elliptical disk with an outer ball bearing. The flexspline is made from thin alloy steel. The spline moves slowly while the wave generator rotates.