Abstract
A two-motor power-split dedicated hybrid transmission (DHT) with two planetary gears is proposed for the applications of a hybrid electric vehicle (HEV) and plug-in HEV (PHEV). The proposed DHT can provide electronically controlled continuous variable transmission (eCVT) with two different gear ratios. One of two electric motors is employed to act as a speeder for splitting the input power of internal combustion engine (ICE) and the other acts as a torquer to assist ICE for boosting. Assisted by an electric motor, ICE can always be enhanced to operate at its efficient area for the benefits of fuel economy improvement. The maximum ICE torque is viable to be mechanically transmitted to vehicle wheels from standstill with two different gear ratios. This feature can help reduce the traction motor torque and power sizing significantly. The paper presents detailed theoretical analyses of the proposed eCVT. Comprehensive simulation demonstrations for a pickup truck HEV application are given to address that the vehicle fuel consumption can be considerably reduced without compromising acceleration performance.
Highlights
Global vehicle manufacturers are demanded to produce more fuel-efficient and low-emission vehicles including electric hybrid vehicles (HEV), plug–in hybrid electric vehicle (HEV) (PHEV) and battery electric vehicles (BEV) in order to satisfy more stringent fuel consumption and emission requirements from global governments
MG1 has zero power split but has to maintain its split torque described in Equation (11) to allow internal combustion engine (ICE) input power directly be transferred to the wheel completely; once MG1 has to run into a positive speed, MG1 starts to consume battery energy in motoring mode to deliver extra positive power adding to existing ICE input power at the powertrain output
Equation (33) indicates that the final gear ratio of ICE torque to the wheel has a completely different k +1 k gain of k +2 1 k f compared to the first gear ratio of 1k k f when motor generator 2 (MG2) is used as the power-split device in the eCVT2 mode
Summary
Global vehicle manufacturers are demanded to produce more fuel-efficient and low-emission vehicles including electric hybrid vehicles (HEV), plug–in HEV (PHEV) and battery electric vehicles (BEV) in order to satisfy more stringent fuel consumption and emission requirements from global governments. HSD will operate in a direct engine drive mode while the traction motor MG2 has to run persistently at a high speed without delivering any active torque assistance and this would cause extra system loss to the hybrid powertrain. Thereby, it will introduce fuel-consumption penalty and not be efficient enough during continuous highway driving. GM dual-mode power-split system can provide 2-geared eCVT functions and result in significant reduction in motor torque and power rating It is much more scalable for HEV applications with different vehicle platforms.
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