HYBRID SYSTEM OF WORKING MACHINE

PROBLEM TO BE SOLVED: To provide a hybrid system of a working machine which can secure a required operating speed without increasing the quantities and capacities of motor generators and pumps, and facilitate mounting on an actual machine. SOLUTION: In the hybrid system, an accumulator circuit 54 supplies pressure fluid accumulated in an accumulator 36 to a suction port of a third pump 6 while accumulating in an accumulator 36 surplus pressure fluid generated in a control valve block 35 of a swivelling motor 7. A return fluid supply circuit 55 supplies return fluid from a control valve block 17 of a boom cylinder 8 to the suction port of the third pump 6. A pressure fluid replenishing circuit 56 replenishes pressure fluid through a discharge port of the third pump 6 to a control valve block 17 of the boom cylinder 8 and a control valve block 18 of an arm cylinder 9. A merging flow control valve 26 is provided between discharge passages of the first pump 3 and of the second pump 4. COPYRIGHT: (C)2007,JPO&INPIT