ABSTRACT
As discussed in Chapter 6, the series–parallel, or more accurately the torque/speed-coupling hybrid drivetrain, has some advantages over the series (electrical coupling) and parallel (single torque or speed coupling) drivetrains. The torque and speed couplings in this drivetrain free the engine from the driven wheels in the torque and speed constraints. Consequently, the instantaneous engine torque and speed can be independent of the load torque and speed of the vehicle. Therefore, the engine can be operated in its high-efficiency region in a similar way as that of the series (electrical coupling) drivetrain.
