Modern methods of synthesis of automatic planetary gearboxes

An increase in the number of gears in automotive transmissions is the most efficient way to reduce fuel consumption and improve the efficiency of automotive vehicles equipped with internal combustion engines. The more gears in the gearbox, the more complicated become the used mechanisms and their number increases as well. The article is devoted to the currently used methods of synthesis and design of automotive multi-speed transmissions consisting of planetary mechanisms. Restrictions on the type of planetary mechanisms used and the number of degrees of freedom of synthesized boxes led to a low efficiency of using mathematical and graphoanalytical methods of synthesis developed in the USSR. Currently analytical synthesis method is an exhaustive search of the possible embodiments of joining planetary mechanisms and control elements. This method provides the possibility of using only single-row three-link planetary mechanisms with correct mathematical description. The second basic way of designing planetary gearboxes is the modular principle of synthesis, which consists in attaching and combining some known and used designs with others. In this case, the main modules are single-row planetary gears with single-pair or pair-wise satellites and planetary gears developed by Simpson and Ravigneaux. Most gearboxes developed by German companies are obtained using this particular approach. The article presents kinematic schemes of gearboxes, currently used in transmissions of modern cars, which are obtained as a result of using the described methods of synthesis.