Patent attributes
A method is provided for transitioning from an initial to a final transmission mode in an electrically variable transmission (EVT), and includes transitioning to an intermediate mode having an additional speed degree of freedom (DOF), changing a transmission ratio, and engaging a clutch to shift to the final mode. The modes include input and compound split, fixed gear ratio, and electric torque converter (ETC), with and without input from an engine. Output torque is maintained by adjusting a charge on an energy storage device. A brake grounds an input member of the EVT. The EVT has the input member, an output member, a stationary member, and first and second motor/generators. An algorithm transitions between modes by releasing at least one clutch to transition to a mode having an extra speed degree of freedom (DOF), and utilizing the extra speed DOF to change the ratio of the EVT.
