Hydraulic system for work machine and hydraulic control method for work machine

摘要

PROBLEM TO BE SOLVED: To provide a hydraulic system of a working machine and a hydraulic control method of the working machine, capable of heating up a control valve in advance to prevent any problem in operation of a spool, by flowing operating oil in the control valve by opening a drain oil path when the control valve is in the neutral position and the temperature of operating oil is predetermined temperature or below.SOLUTION: The hydraulic system includes a discharge circuit 4 of a variable displacement pump 3 whose pump discharge rate Q is adjustable, an actuator 6 connected with the discharge circuit 4 via a control valve 5, and a controller 7 for controlling pump discharge pressure of the variable displacement pump 3, and the controller 7 controls the discharge circuit 4 so that command discharge pressure corresponding to a predetermined bleed-off area value calculated from the operation amount of the control valve 5 is produced therefrom. The hydraulic system includes an oil flowing means 10 for flowing operating oil in the control valve 5 by opening a drain oil path 9 for discharging operating oil in the discharge circuit 4 through the control valve 5 to an operating oil tank 8, when the control valve 5 is in the neutral position and temperature of operating oil is predetermined temperature T or below.