Design of high-contact-ratio spur gears using quadratic parametric tooth profiles

In order to obtain high contact ratios, the addendums of spur gears with involute profiles should be increased. This will increase the root stress sensitivity and the minimum tooth number of gears without undercut. This paper proposes a method of designing high-contact-ratio spur gears using quadratic parametric tooth profiles for the shorter addendums and no undercut. A design procedure is developed and a simplified derivation of the mathematical model of parametric tooth profiles is presented. The tooth root stresses and the static transmission errors are shown to be lower than those of high-contact-ratio spur gears with involute profiles, but the contact stresses and the wear height indices are traded off. Some examples are given to demonstrate the potential of this method. (C) 1998 Elsevier Science Ltd.