HYBRID SYSTEM FOR WORKING MACHINE

PROBLEM TO BE SOLVED: To provide a hybrid system for a working machine, easy to mount on an actual machine while securing a required operating speed without increasing the number and capacity of each of a motor/generator and a pump. SOLUTION: An accumulator circuit 54 accumulates in an accumulator 36 pressure fluid generated in a control valve block 35 of a turning motor 7 and supplies the accumulated pressure fluid to a suction port of a third pump 6. An accumulator flow control valve 45 and a check valve 46 are installed in a passage branching in front of a bypass flow control valve 44 which is provided in a bypass passage in the third pump 6 separately from the accumulator circuit 54 from a turning motor circuit 53. A return fluid supply circuit 55 supplies return fluid from a boom cylinder circuit 51 to the suction port of the third pump 6 during down-booming. A pressure fluid resupply circuit 56 resupplies the pressure fluid from a discharge port of the third pump 6 to the boom cylinder circuit 51 and an arm cylinder circuit 52. COPYRIGHT: (C)2007,JPO&INPIT