The Micro Harmonic Drive components — welcome to the realm of the rings

The flat-type design of Micro Harmonic Drive Gear consists of a Wave Generator and three gear wheels — Flexspline, Circular Spline and Dynamic Spline.

 

 

 

 

The Wave Generator

consists of a sun gear, usually attached to the motor's shaft, and two elastically resilient planetary gears. The teeth on the planetary gears also mesh with the inner teeth of the Flexspline.

 

The Flexspline

is a thin-walled, elastic ring that takes on an elliptical shape because of the Wave Generator. The outer teeth are meshing with the inner teeth of the Circular and the Dynamic Spline.

 

The Circular Spline

is a internal gear. Its teeth mesh with the outer teeth of the Flexspline at both ends of the major
elliptical axis of the Wave Generator. The Circular Spline has two more teeth than the Flexspline.

 

The Dynamic Spline

is a internal gear. Its tooth-count is the same as the Flexspline's . It rotates in the same direction and at the same speed as the Flexspline and is used in speed reduction configurations as the output element.

 

 

 

Wave Generator types

 

Design with advantages

In Micro Harmonic Drive Gears, the Wave Generator is formed by a planetary gear stage, a design with many advantages:

• all gear components are produced with a highly-precise LIG process

• minimal assembly overhead with only three components (four for i = 120)

• a large range of variations for overall gear reduction ratio

• convenient adaptation of very high rotary speeds to specific requirements

• very low moment of inertia for highly dynamic acceleration and positioning action

 

Everything in proper proportion

Overall reduction ratio for the Micro Harmonic Drive Gear is determined by a combination of the Wave Generator's planetary gear stage, the tooth-count of the Flexspline and the tooth difference between the Circular Spline and Flexspline. Greater tooth-differences between Circular Spline and Flexspline lessens overall reduction.

The Harmonic Drive design for micro gears can accommodate a wide range of different reduction ratios by virtue of

• a Wave Generator with 2 planetary gears for i = 160, i = 500 und i = 1000

• a Wave Generator with 3 planetary gears for i = 120.

 

Resilient planetary gears for more precision

The planetary gears in the Micro Harmonic Drive Gear are another reason for the design's zero backlash and precise behaviour. These gears are thin-walled rings which possess both sufficient flexibility and stiffness. They are slightly bent into an elliptical shape in the radial direction during assembly, thus they produce a radial pretension in the gear unit. This elastic pretension in the planetary gear stage eliminates backlash between planetary gear teeth flanks, equalises tooth wear and produces the desired, exact deformation of the Flexspline.

 

 

 

Micro gearboxes

 

 

Simply connect

To simplify integration of the gear system into a machine or product environment, the Micro Harmonic Drive Gear is only available as a gearbox. Depending on the application, the gearbox can either be combined directly with common micro motors or — if the gearbox is a variant with input shaft — the motor can be attached axially. The optional hollow shaft can be used as a passageway for laser beams, optical fibres or for vacuum supply through the centre axis of the gearbox.

 

The special features

• Zero backlash Micro Harmonic Drive gear component set

• Preloaded bearings for input and output shafts

• Housing and shafts made of stainless steel

• Hollow shaft (optional) permits passage of laser beams, optical fibres, compressed air or vacuum

• Lifetime lubrication

 

Advantages of the Micro Harmonic Drive

• Precise

• Fast

• Reliable

• Robust

• Versatile