Abstract: In order to increase bending load capacity, a new-style asymmetric gear with different pressure angles is designed and involute profile equations and transition curve equations of tooth root of driving side and coast side for asymmetric gear are proposed. Through iteration algorithm and optimization strategy, the analytic calculation formula of tooth root bending stress for asymmetric gear is presented. Based on parametric programs of total tooth profile, a finite element model for asymmetric gear is built. By analytic calculation of tooth root bending stress and dangerous section position for several combinations of pressure angles, the results show that the maximum tensile stress at the tooth root decreases and single tooth mesh area moves towards tooth tip with increase of pressure angle of driving side. The calculation results using finite element method are similar to analytic method and the formula for tooth root bending stress vs. pressure angle of asymmetric gear is determined by the least squares method. By wire electrical discharge machining, the symmetric gear and asymmetric gear are manufactured and bending fatigue strength testing is carried on the HF fatigue-testing machine. The testing result shows that limit load of asymmetric gear increases about 50% on the same tooth life compared with symmetric gear and the bending stress transformation of tooth root is similar to the calculation results of analytic method and finite element method.

Key words: Asymmetric gear, Double pressure angle, Fatigue strength, Finite element analysis, Gear transmission