| 摘要 |
PROBLEM TO BE SOLVED: To fully recover the energy of the pressure oil discharged from a hydraulic pump to effectively utilize the same, when all of direction selector valves are located on their neutral positions. SOLUTION: A center by-pass circuit 11 positioned at the downstream of a plurality of direction selector valves 3b, 4b is provided with devices 6, 7 for converting the energy of the pressure oil flowing into a tank 12 through the center by-pass circuit 11, into electric energy. The energy of the whole pressure oil flowing into the tank 12 through the center by-pass circuit 11 is recovered as electric energy, when operation levers of all of hydraulic actuators are not operated, and all of direction selector valves are located on their neutral positions, whereby the electric energy can be regenerated and utilized as various energies, which improves the consumption efficiency of the energy of the pressure oil generated in the hydraulic pump. |
