An engine idling control method for a construction machine includes setting, by an E-ECU, an initial engine RPM as a starting mode (S mode) by receiving a signal from a V-ECU at the time of an engine startup; receiving, by the E-ECU, a first instruction via an engine speed control switch in a state other than an automatic idle mode; activating the automatic idle mode when the first instruction is not input to a machine during a certain time period, and setting the engine RPM as the starting mode (S mode); deactivating the automatic idle mode when a second instruction is input to the machine via the engine speed control switch while the automatic idle mode is activated; and calculating, by the V-ECU, an actual torque required for a pump for starting the machine according to the second instruction when the automatic idle mode is deactivated, and sending the actual torque to the E-ECU.

A hydraulic excavator 1 includes an engine 16, a main hydraulic pump 17 driven by the engine 16, a plurality of hydraulic actuators driven with pressure oil discharged from the main hydraulic pump 17, a plurality of flow rate control valves adapted to control the flow rate of pressure oil to be supplied from the main hydraulic pump 17 to the respective hydraulic actuators, a pilot hydraulic pump 18 adapted to supply pressure oil for driving the flow rate control valves, and a controller 15 configured to control the discharge flow rate of the pilot hydraulic pump 18. The controller 15 controls the discharge flow rate of the pilot hydraulic pump 18 such that it becomes equal to the sum of requested pilot flow rates determined in accordance with control commands for the respective flow rate control valves and a preset standby flow rate.

A joystick pilot valve equipped with the structure for preventing oil leakage comprises: a valve body; spool installed in the valve body to be moved between the supply port and the hydraulic fluid chamber; spool hole installed in the valve body; pushing cam connected to the upper portion of the valve body by joint; joystick lever connected to the pushing cam to make the pushing cam move like seesaw by the operation and make the spool move in the spool hole forward and backward to make the supply port connected or disconnected to the hydraulic fluid chamber; outer boot provided at the valve body to cover the outer periphery of the valve body, the pushing cam and the joystick lever; inner boot arranged inside of the outer boot and forming oil leak storage chamber sealed from the outer side at the upper portion of the guide hole.

A working machine including a movable implement, a hydraulic actuator for displacing the implement, and a hydraulic control system for enabling an operator to control movement of the implement. The control system allows the implement to be returned to a desired position or state, such as a return to dig position or a return to float state, in a single automated operation that is initiated by the operator actuating a switch at the same time as moving a joystick in a desired direction. A pilot-operated valve is used to supply hydraulic fluid under pressure to the actuator acting on the implement and the operation of the joystick is detected by means of a pressure sensor connected to a control line of the pilot-operated valve.

There is provided a fluid circuit capable of continuously driving pressure-increasing devices with a simple configuration. A plurality of pressure-increasing devices are connected in parallel to a fluid supply device that delivers a working fluid. A stroke direction of the piston of each of the pressure-increasing device is switched by the working fluid. A phase of the piston of one pressure-increasing device is different from a phase of the piston of the other pressure-increasing device.