In this article, a Dedicated Hybrid Transmission (DHT) with one electric machine (EM) and a 4-speed DCT is described and investigated. The EM is connected to the input shaft of the 4- speed DCT trough a planetary gear set (PGS) and two shifting elements. The 4-speed DCT is part of a modular 8-speed DCT and can be derived by removing one drive shaft with the gears 1, 2, 3 and 8. Since the EM and the PGS are utilized for launching the vehicle, a wet clutch is not necessary. The 4-speed DHT is compared to a P2 8-speed DCT with focus on the mechanical transmission losses. To achieve this, a transmission loss calculation developed by the Institute of Automotive Engineering (IAE) is utilized, which allows a detailed analysis of the various loss components. The results show an increase of the average transmission efficiency in WLTP which is achieved by less mechanical components and waiving of the wet shifting elements. Since the recuperation efficiency benefits from higher transmission efficiency, the overall fuel and energy consumption is improved by approximately 3 % both in hybrid and electric operation.
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