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    • 4. 发明公开
    • CONSTRUCTION MACHINERY
    • EP3995632A1
    • 2022-05-11
    • EP20870184.7
    • 2020-06-12
    • Hitachi Construction Machinery Tierra Co., Ltd.
    • ISHII TakeshiTAKAHASHI Kiwamu
    • E02F9/20E02F9/22
    • A construction machine is provided which is capable of detecting an operation state of an operation device even if the idle rotation speed for a prime mover is set to a low value and is capable of setting the idle rotation speed for the prime mover to a low value. A hydraulic excavator includes an operation device that generates a pilot pressure corresponding to an operation amount of an operation lever and switches a control valve with the generated pilot valve, and a controller that controls an electric motor such that the rotation speed of the electric motor becomes an idle rotation speed set in advance when a no-operation state of the operation device continues. The hydraulic excavator further includes a hydraulic pressure signal line that is connected between the discharge side of a pilot pump and a tank and in which the control valve is interposed, a fixed restrictor provided between the discharge side of the pilot pump and the control valve in the hydraulic pressure signal line, and pressure sensors that individually detect the hydraulic pressures on the upstream side and the downstream side of the fixed restrictor. The controller detects an operation state of the operation device on the basis of results of detection of the pressure sensors.
    • 6. 发明公开
    • HYDRAULIC DRIVE DEVICE FOR CONSTRUCTION MACHINE
    • EP3591239A1
    • 2020-01-08
    • EP18908261.3
    • 2018-03-28
    • Hitachi Construction Machinery Tierra Co., Ltd.
    • TAKAHASHI KiwamuMAEHARA TaiheiISHII Takeshi
    • F15B11/05E02F9/22
    • Even where the differential pressure across a directional control valve associated with each actuator is very small, flow dividing control of the plurality of directional control valves can be performed stable, and even where a demanded flow rate suddenly changes at the time of transition from composite action to single action or the like, a sudden change of the flow rate of hydraulic fluid to be supplied to each actuator is prevented to implement superior combined operability. Further, the meter-in loss of the directional control valves can be reduced to implement a high energy efficiency. To this end, a plurality of pressure compensating valves 7a, 7b and 7c for controlling such that the pressure in the downstream side of the meter-in opening of a plurality of directional control valves 6a, 6b and 6c becomes equal to the highest load pressure are individually arranged in the downstream side of meter-in openings of the plurality of directional control valves 6a, 6b and 6c, and demanded flow rates for the directional control valves 6a, 6b and 6c are calculated from input amounts of operation levers. Besides, the meter-in pressure loss of a predetermined directional control valve is calculated from the demanded flow rates for and meter-in opening areas of the directional control valves 6a, 6b and 6c, and the set pressure of the unloading valve 15 is controlled using the value of the meter-in pressure loss.