The ever-increasing demands for vehicle emission control have resulted in an expansion of planetary gearbox applications in road vehicles, due to their possibility to change the transmission ratio under load in synchronism with engine operation. Modern boxes are designed to extract the maximum number of transmission ratios as possible from the least possible number of simple component planetary gear trains (PGTs). The application demands dictate whether the box will be built with the maximum number of transmission ratios, or built for ruggedness and reliability. Component interconnections are designed to avoid power circulation, hollow shafts, or complex planet carrier arrangements when possible. The subject of this paper are multi-speed complex planetary gearboxes having at least two interconnected simple component PGTs controlled by brakes and clutches. Several variants of complex PGTs are examined together with the placement of brakes and clutches on their external shafts, and their transmission ratio functions are derived. The kinematics of multi speed gear trains are analysed as combinations of two or more two-speed gear trains. Several gearbox layouts are analysed, and their transmission ratio functions provided. Finally, an overview of the procedure for the calculation of creation of multi-speed gear trains is provided.
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Vrcan et al. (2024) studied this question.
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