HYDROMECHANICAL GEARBOX

The invention relates to hydromechanical gearboxes applied to a driving vehicle. The hydromechanical gearbox includes a stage planetary reduction gear and is controlled by an electronic system and a hydraulic system, and the hydromechanical gearbox realizes nine forward motion gears and one reverse motion gear and comprises a casing, an input member, an output member, a hydrodynamic torque converter, and a planetary reduction gear comprising four planetary gear sets, three controllable brakes and three controllable clutches. In the planetary reduction gear, a first planetary gear set includes a sun wheel (3), a planet carrier (2), and a gear ring (1), a second planetary gear set includes a sun wheel (6), a planet carrier (5), and a gear ring (4), a third planetary gear set includes a sun wheel (9), a planet carrier (8), and a gear ring (7), and a fourth planetary gear set includes a sun wheel (12), a planet carrier (11), and a gear ring (10). The input member (20) is connected with the gear ring (10) of the fourth planetary gear set and the planet carrier (8) of the third planetary gear set through a clutch (16). The input member (20) is connected with the output member (22) of the hydrodynamic torque converter and is connected with the sun wheel (12) of the fourth planetary gear set via a clutch (17). The sun wheel (6) of the second planetary gear set is connected with the input member (20). The output member (21) is connected with the planet carrier (11) of the fourth planetary gear set and the gear ring (7) of the third planetary gear set that are connected each other. A brake (14) connects the gear ring (1) of the first planetary gear set and the planet carrier (5) of the second planetary gear set that are connected with each other to a gearbox casing (19). A brake (13) connects the sun wheel (3) of the first planetary gear set to the gearbox casing (19). A brake (15) connects the planet carrier (8) of the third planetary gear set and the gear ring (10) of the fourth planetary gear set that are connected with each other to the gearbox casing (19). A clutch (18) connects the gear ring (4) of the second planetary gear set with the planet carrier (2) of the first planetary gear set and the sun wheel (9) of the third planetary gear set that are connected with each other.