Power transmission apparatus for vehicle

A power transmission apparatus for a vehicle comprising:

• a first input shaft selectively connected to an engine output shaft through a first clutch;
• a second input shaft configured as a hollow shaft that is disposed on the outer circumference of the first input shaft without rotational interference and selectively connected to the engine output shaft through a second clutch;
• a third input shaft configured as a hollow shaft that is disposed on the outer circumference of the second input shaft without rotational interference and selectively connected to the engine output shaft through a third clutch;
• an output shaft placed parallel to the first, second, and third input shafts at a certain distance;
• a power transmission shaft configured as a hollow shaft that is disposed on the outer circumference of the output shaft without rotational interference and selectively connected to the output shaft through a fourth clutch;
• a motor/generator that drives the first input shaft;
• a planetary gear set has three rotational elements, one of which being fixedly connected to the power transmission shaft and another being fixedly connected to the output shaft;
• and
• three speed gear sets disposed between the first, second, and third input shafts and the power transmission shaft and remaining rotational element of the planetary gear set, with drive gears and driven gears externally gear-meshed to each other.