HYDRAULIC SYSTEM OF A TRANSMISSION UNIT, COMPRISING A MAIN TRANSMISSION PUMP AND AN AUXILIARY PUMP

摘要

The invention relates to a hydraulic system (1) of a transmission unit (2) comprising a main transmission pump which can be driven by a torque applied via the transmission unit and an auxiliary pump (7) which can be driven by an electrical machine (6), the two pumps supplying a primary pressure circuit (3) and a secondary pressure circuit (8) with hydraulic fluid depending on the operational state. A pressure side of the main transmission pump and a pressure side of the auxiliary pump (7) are connected to the primary pressure circuit (3) upstream of a pressure relief valve (9) which adjusts a main pressure (pHD) of the primary pressure circuit (3). The pressure relief valve (9) is arranged between the pressure sides of the main transmission pump (4) and the auxiliary pump (7) and the secondary pressure circuit (8). The pressure side of the auxiliary pump (7) can be actively connected to the secondary pressure circuit (8) via a hydraulic line (L1) which can be blocked in the direction of the primary pressure circuit (3) and the secondary pressure circuit (8) and which by-passes the pressure relief valve (8).