| 摘要 |
PROBLEM TO BE SOLVED: To prevent an overload of an engine due to increase of the output of a hydraulic pump, and to improve the upward slope traveling ability in the case of singly operating traveling of a vehicle without performing a combined operation. SOLUTION: The input torque from the engine 30 to four hydraulic pumps 32-35 is set at 1/4 in the normal standard input torque condition, and in order to increase to 1/2 to switch the torque condition to a high input torque condition when singly operating the traveling of a vehicle, shuttle valves 47 and 48 are connected to a pilot valve 46 and pilot valves 44 and 45, and the highest pressure is taken out by pressure sensors 49 and 50. Pressure signals from the pressure sensors 49 and 50 are taken into a controller 51. When an output level H of the pressure sensor 49 and an output level L of the pressure sensor 50 are detected, pressure is supplied from a booster pump 56 to increased output ports 52a-55a provided in regulators 52-55 of each hydraulic shovel 32-35 to increase the input torque from the engine 30 to the hydraulic pumps 32-35.
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