Dimensional Synthesis of a Dedicated Hybrid Transmission Through Efficiency Optimization of Gear Trains

Abstract

Hybridization is a promising solution to reduce regulated emissions without compromising vehicle’s performance, what makes the development of transmission systems for hybrid electric vehicles a relevant and prolific study field. Inside this scenario, one new transmission category emerges: the Dedicated Hybrid Transmission (DHT), which includes transmission systems that use at least two sources of propulsion, an internal combustion engine and at least one electric motor, and whose functionality depends on both propulsion sources. One important aspect to be studied is the gear trains’ mechanical efficiency of DHTs. In this paper, a DHT available on the market was selected as a case study to apply a technique of dimensional synthesis focusing on efficiency. The technique is based on an electromechanical analogy associating graph and screw theories with Kirchhoff laws. The objective is to optimize the DHT’s efficiency by altering the gears’ pitch radii, seeking to reduce the consumption of a vehicle under city driving conditions.