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A simplified analysis is presented in order to evaluate the influence of the profile modifications minimising transmission error time-variations on some other key design criteria such as mesh forces, stresses and tooth friction losses. A unique equation for the set of profile modification rendering transmission error nearly constant is presented and a number of original stress and loss factor closed-form formulae are derived whose results compare very well with those obtained by numerical simulations. Some general results are then deduced about the evolutions of the design criteria with regard to optimum relief parameters which are believed to be useful at the early stage of profile modification design. [ABSTRACT FROM AUTHOR]

Abstract: For increasing the load carrying capacity of geared power transmissions several tooth designs alternative to the standard involute have been proposed. The use of non-involute teeth has a number of disadvantages and for this reason asymmetric involute-type teeth have been studied as a promising alternative. In this paper the idea of one-sided involute asymmetric spur gear teeth is introduced to increase load carrying capacity and combine the good meshing properties of the driving involute and the increased strength of non-involute curves. These novel teeth are intended for constant direction of rotation although they can be used in a limited way for reverse rotation. Both flanks are fully generated by a hob, the design of which is also investigated. The increase in load carrying capacity can reach up to 28% compared to the standard 20° involute teeth. [Copyright &y& Elsevier]

Abstract: This paper investigates effect of addendum on tooth contact strength, bending strength and basic performance parameters of spur gears. Face-contact model of teeth, mathematical programming method (MPM) and three-dimensional (3D), finite element method (FEM) are used together to conduct loaded tooth contact analyses (LTCA), deformation and stress calculations of spur gears with different addendums and contact ratios. Tooth load, load-sharing rate, contact stress, root bending stress, transmission error and mesh stiffness of the spur gears are analyzed. Effects of addendum and contact ratio on gear strength and basic performance parameters are also discussed. It is found that contact stress distributed on tooth surface along the profile is asymmetrical around the geometrical contact point of the gears when the geometrical contact point is far away from the pitch point, especially at the tip or root contacts. The maximum contact stress is also not exactly at the geometrical contact point. Hertz formula can only calculate the tooth contact stress approximately. FEM can be used to conduct precise analysis of the tooth contact stress. It is also found that increment of addendum can increase number of contact teeth, then this increment can reduce tooth contact stress and root bending stress, generally speaking. But this increment also makes the tooth depth long and lets the tooth be deformed easily. So, this increment can reduce tooth contact stress, but there is no guarantee that this increment can certainly reduce tooth root bending stress. Also, increment of the addendum makes the values of “T” and “V” in the so-called value of “PVT” great. So, scoring strength calculations of the tooth tip and root becomes more important when to use high contact ratio gears (HCRG) with long addendum. Finally, strength calculations of HCRG with misalignment error, lead crowning and thin-walled thickness are discussed simply in this paper. [Copyright &y& Elsevier]

• The tip contour of a protuberance hob is defined in detail by a Bezier curve with six parameters. • Hob tip contour is optimized for increasing the bending capacity of gear tooth root. • A best set of Bezier curve parameters for usually standard hobs is found out for reducing the tooth root stress. • A best set of Bezier curve parameters for protuberance hobs is found out for reducing the tooth root stress. • These two sets of parameters are widely applicable to all common gear cases. Optimising the hob used to manufacture gears is an attractive approach for minimizing the gear tooth root stress. However, currently available approaches often require modifying the hob for every gear case, which limits their practical application and increases design and manufacturing costs. In this study, two sets of Bezier curve parameters for gear hobs were developed to minimize the tooth root stress: one for standard hobs and the other for protuberance hobs. The two parameter sets can be used to modify any hob and effectively reduce the gear bending stress, and they are widely applicable to all common gear cases. Calculation with the finite element method indicated that the first-best parameter set for standard hobs reduced the stress of most gear cases by 6%–10%. The second-best parameter set for protuberance hobs reduced the stress of almost all gear cases by 7%–15%. The average optimisation potential was 10.73%. Meanwhile, the manufacturing cost is very low because an optimised hob can be applied to producing other gears. These two parameter sets are a significant contribution to the optimisation and manufacture of gears. [ABSTRACT FROM AUTHOR]