Lexus developed the Multi Stage Hybrid Transmission for the flagship Lexus LC500h coupe with the aim of achieving an excellent balance between fuel economy and acceleration performance. To gain these benefits, this transmission utilizes a multi-stage approach with the input split mode as an enabler for a concept of multiple high- efficiency points. In order to apply this approach to the transmission, a shift device was located immediately after a power split device. For functioning of the input split mode electrically-controlled continuously variable transmission, the power split device is connected with the motor, generator, and inverters. The optimal gear selection of the shift device to reduce the power loss in accordance with the driving state improves not only fuel economy but also heat management performance compared with the previous hybrid transmission. The Lower gears of the shift device that amplifies both the motor and the engine torque enhances acceleration performance compared with the previous hybrid transmission which amplifies only the motor torque. This paper describes the motivation for selecting the multi-stage approach with the input split mode from implementations of multiple high-efficiency points concept, and the potential of multi-stage approach with the input split mode compared to the previous hybrid transmission.
Citation: Imamura, T., Tabata, A., Matsubara, T., Iwase, Y. et al., 'Concept and Approach of Multi Stage Hybrid Transmission,' SAE Technical Paper 2017-01-1098, 2017, https://doi.org/10.4271/2017-01-1098.
The hybrid manual transmission 6BMT215 concept offers specific advantages for small and mid-size powertrains as a cost efficient option to create mild hybrid variants based on a 48 V electric system. By using a standardized hybrid part component kit shared with hybrid DCTs, cost and development risks are minimized. The EVplus solution, with a plug-in hybrid technological feature, is an improvement over ZF Friedrichshafen’s current eight-speed automatic transmission. With a fully integrated electric transmission, the maximum output of this novel hybrid solution will be 160 kW, or more than 215 horsepower.
Author(s): Tatsuya Imamura, Atsushi Tabata, Tooru Matsubara, Yuji Iwase, Kenta Kumazaki, Keita Imai
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