US Patent 10569639 Power transmission system of hybrid electric vehicle

A power transmission system of hybrid electric vehicle may include an engine, a motor/generator, an input unit including a first input shaft, a second input shaft separately disposed on a same shaft as the first input shaft and an end portion of the second input shaft selectively connectable with the first input shaft in a state of being directly connected with the output side of the motor/generator, a first middle shaft disposed surrounding the first input shaft without rotational interference with the first input shaft to be selectively connectable with the first input shaft, and a second middle shaft including a hollow shaft and disposed surrounding the second input shaft without rotational interference with the second input shaft to be selectively connectable with the second input shaft, and an output shifter shifting torque of the input unit and outputting the shifted torque.