THE KINEMATICS AND STRENGTH OF BIHARMONIC GEAR DRIVES

The biharmonic gear drive has a thin walled cylindrical flexible gear with teeth on both the outer and inner surface. The flexible gear is c onstrained from outside by a wave generator bearing to an oval shape. The outer teeth of the flexible gear engage with a concentric outer ri gid circular gear across the major axis of the oval. The inner teeth e ngage with a concentric inner circular gear across the minor axis. The outer rigid gear is fixed to the ground. The outer ring of the wave g enerator roller bearing is the input member and the inner rigid gear t he output member of the drive. An accurate method for kinematic analys is of the engagement conditions was developed, This method could be us ed to create error free meshing tooth profiles conjugate to given prof iles of the flexible gear. The concept of continuous meshing was defin ed, New continuously meshing tooth profiles were developed. Continuous ly meshing teeth are constantly in contact with their counterteeth thu s giving radial support to the wall of the flexible gear. These profil es have no risk of detrimental tooth tip interference. Finite element strength analyses of biharmonic drive models with, correspondingly, in volute and continuously meshing tooth profiles were carried out. The g eometry of drive models with continuously meshing tooth profiles was o ptimized in regard to stiffness and fatigue. The torsional stiffness, fatigue strength, and vibrational behavior of biharmonic drives were c ompared to those of conventional harmonic drives. The method developed covers the whole span from kinematics to strength of biharmonic drive s. It is a convenient tool for the study and design of biharmonic driv es. It is also applicable to conventional harmonic drives.