Patent ID: 8840503

Claim:
A hydrostatic mechanical transmission comprising: a hydrostatic transmission which transmits power generated in an engine using a pump and a motor; a main transmission unit which transmits the engine power to a final driving unit through a driving shaft; a complex planetary gear which synthesizes and transmits the engine power transmitted from the hydrostatic transmission and the main transmission unit; and an automatic manual sub-gearshift which receives the synthesized engine power from the complex planetary gear so as to perform a transmission function and transmits the engine power to the final driving unit, wherein the automatic manual sub-gearshift includes: a synchro-transmission which receives the synthesized engine power from the complex planetary gear so as to perform a transmission function; and clutch which selectively intermits the engine power transmitted from the synchro-transmission and transmits the engine power to the final driving unit, wherein the engine power synthesized in the complex planetary gear is transmitted to a sun gear or a carrier, and the synchro-transmission receives the engine power from the sun gear or the carrier so as to perform a transmission function, wherein the synchro-transmission includes: a first synchro-transmission which selects a first-stage sub-gearshift gear set or third-stage gear set and transmits to the output shaft; and a second synchro-transmission which selects a second-stage sub-gearshift gear set or a reversing gear set and transmits rower to the output shaft.