Abstract: A construction machine capable of achieving favorable operability in a combined operation is provided. A hybrid excavator includes: a boom cylinder 10 driven by hydraulic fluid from a hydraulic pump 16b; a swing hydraulic motor 5 driven by hydraulic fluid from the hydraulic pump 16b; a swing electric motor 6 connected mechanically with the swing hydraulic motor 5; an inverter 19 that controls operation of the swing electric motor 6; and a controller 21 that outputs to the inverter 19 a torque command value for controlling electric driving torque or electricity generating torque of the swing electric motor 6.

Abstract: It becomes possible to prevent deterioration of an electric storage device due to overdischarge of the electric storage device and engine stalling due to insufficient assist or disabled assist when a charge amount of the electric storage device falls, ensure that work is continuously conducted, suppress an operator from feeling discomfort in operation, and ensure favorable operability. A pump target output power computing section (21) computes present pump demanded power on the basis of work related information, limits the present pump demanded power in response to a degree of reduction of a state of charge of an electric storage device (12a) when the state of charge is lower than a preset threshold, and computes the limited present pump demanded power as present pump target output power.

Abstract: A hydraulic system for a work machine includes a first hydraulic pump driving a swing hydraulic motor; a second hydraulic pumps driving a boom cylinder; a first pump displacement increase valve controlling a volume of the first hydraulic pump; a swing pilot pressure sensor detecting a swing operation amount; a boom raising pilot pressure sensor detecting a boom raising operation amount; and a controller controlling a control signal to the first pump displacement increase valve on the basis of the swing operation amount and the boom raising operation amount. The controller controls the control signal in such a manner that a delivery rate of the first hydraulic pump becomes higher as the swing operation amount is larger and an increasing rate of the delivery rate of the first hydraulic pump becomes lower as the boom raising operation amount is larger during a swing boom raising operation.

Abstract: A hydraulic control system achieves a reduction in meter-out pressure loss in accordance with variation of a negative load acting on a hydraulic actuator. A hydraulic fluid discharged from the actuator flows through meter-out flow lines having variable restrictors. A load sensor detects the magnitude of a negative load applied to the actuator by an external force in the same direction as the operating direction of the actuator. A control device reduces the sum total of the opening areas of the variable restrictors in accordance with an increase in the magnitude of the negative load detected by the load sensor and the operation amount detected by the operation amount sensor when the load abnormality sensor does not detect any abnormality. When an abnormality is detected, it reduces the sum total of the opening areas to a predetermined value in accordance with the operation amount detected by the operation amount sensor.

Abstract: A hybrid work machine that can suppress excessive limiting on pump absorption power even in a situation in which supply of electric power to an electric motor is limited is provided. The hybrid work machine includes: an engine 22; an assist generator motor 23 connected to the engine 22 in such a manner that a torque can be transmitted to the engine 22; an electric storage device 24 that supplies electric power to the assist generator motor 23; a monitoring device 28 that monitors the electric storage device 24 and that acquires electric storage device information; a hydraulic pump 41 driven by the engine 22 and the assist generator motor 23; and a pump regulator 43 that regulates a delivery flow rate of the hydraulic pump 41.

Abstract: A work machine pump control system includes: a pump horsepower control valve (22) which causes a first urging force determining a limited horsepower (F) of a hydraulic pump and a second urging force due to a delivery pressure of the hydraulic pump to act on a spool in opposition to each other and which controls the pump flow rate such that it does not exceed the limited horsepower (F); a target pump flow rate computation section (42) computing a target pump flow rate based on an operation pressure (px) and a load pressure (py); a target horsepower computation section (41) which computes a required horsepower (Freq) corresponding to an operation pressure (px) from a relationship related to the operation pressure (px) and which computes a target horsepower (Ftar) based on the required horsepower (Freq); and a pump horsepower control section (35) which controls the pump horsepower control valve (22) such that the target pump flow rate (Qtar) is delivered with the limited horsepower (F) determined by the pump hor

Abstract: A motor-generator (27) is connected mechanically to an engine (21) and a hydraulic pump (23). The hydraulic pump (23) delivers pressurized oil to cylinders (12D) to (12F) in a working mechanism (12), a traveling hydraulic motor (25) and a revolving hydraulic motor (26). The revolving hydraulic motor (26) drives a revolving device (3) in cooperation with a revolving electric motor (33). An HCU (36) reduces outputs of the revolving electric motor (33), the revolving hydraulic motor (26), the boom cylinder (12D) and the like such that a ratio of a revolving speed of an upper revolving structure (4) and a movement speed of raising a boom (12A) is held to a ratio in a normal mode (NMODE) at the time of performing a compound movement of a revolving movement and a boom-raising movement in a low speed mode (LSMODE).

Abstract: Disclosed is a hydraulic drive system capable of improving the fuel efficiency of a work machine by reducing the pressure loss and drag loss of a hydraulic pump. There are provided an electric motor M; a third pump P3 driven by the electric motor; a third pump hydraulic line L3 to which the delivered hydraulic fluid from the third pump is supplied; a third directional control valve V4 provided in the third pump hydraulic line, switch-operated by an arm operation device 19, and controlling the flow rate of the hydraulic fluid supplied to the arm cylinder 8 from the third hydraulic pump; and a controller 18 drive-controlling the electric motor, wherein the controller drives the third pump by the electric motor when a swing/arm combined operation is detected by pilot pressure sensors S6, S7, S10, S11.

Abstract: A work machine includes directional control valves 43 and 44 each controlling a direction and a flow rate of a pressurized fluid supplied to each a boom cylinder 32 and a bucket cylinder 36; operation amount sensors 51a, 52a, and 52b detecting operation amounts of operation devices 51 and 52; a variable flow control valve 45 that can restrict the flow rate of the pressurized fluid in a meter-in passage of the directional control valve 44 related to the bucket cylinder 36; and a controller 60 controlling the variable flow control valve on the basis of the detection results by the operation amounts from the operation amount sensors, and the controller changes over an action mode to any one of a normal mode for restricting the flow rate of the pressurized fluid by the variable flow control valve and a responsiveness priority mode for not restricting the flow rate of the pressurized fluid by the variable flow control valve in response to the detection results of the operation amounts of the plurality of operation

Abstract: A hydraulic excavator is equipped with: an arm cylinder driven by a hydraulic working fluid from a hydraulic pump; a meter-out passage through which the hydraulic working fluid discharged from the arm cylinder flows; a control valve controlling the hydraulic fluid flow rate of the meter-out passage; a pressure sensor detecting a load acting on the arm cylinder; a pressure sensor detecting an operation amount of an operation device operating the arm cylinder; and a controller. The controller alternatively selects a normal operation mode in which the opening area of the control valve is controlled based on an actuator load and the operation amount, and a substitution operation mode in which the opening area of the control valve is controlled based on the operation amount. When the substitution operation mode is selected, a delivery flow rate of the hydraulic pump is further increased as compared with the normal operation mode.

Abstract: It becomes possible to prevent deterioration of an electric storage device due to overdischarge of the electric storage device and engine stalling due to insufficient assist or disabled assist when a charge amount of the electric storage device falls, ensure that work is continuously conducted, suppress an operator from feeling discomfort in operation, and ensure favorable operability. A pump target output power computing section (21) computes present pump demanded power on the basis of work related information, limits the present pump demanded power in response to a degree of reduction of a state of charge of an electric storage device (12a) when the state of charge is lower than a preset threshold, and computes the limited present pump demanded power as present pump target output power.

Abstract: A work machine pump control system includes: a pump horsepower control valve (22) which causes a first urging force determining a limited horsepower (F) of a hydraulic pump and a second urging force due to a delivery pressure of the hydraulic pump to act on a spool in opposition to each other and which controls the pump flow rate such that it does not exceed the limited horsepower (F); a target pump flow rate computation section (42) computing a target pump flow rate based on an operation pressure (px) and a load pressure (py); a target horsepower computation section (41) which computes a required horsepower (Freq) corresponding to an operation pressure (px) from a relationship related to the operation pressure (px) and which computes a target horsepower (Ftar) based on the required horsepower (Freq); and a pump horsepower control section (35) which controls the pump horsepower control valve (22) such that the target pump flow rate (Qtar) is delivered with the limited horsepower (F) determined by the pump hor

Abstract: A construction machine capable of achieving favorable operability in a combined operation is provided. A hybrid excavator includes: a boom cylinder 10 driven by hydraulic fluid from a hydraulic pump 16b; a swing hydraulic motor 5 driven by hydraulic fluid from the hydraulic pump 16b; a swing electric motor 6 connected mechanically with the swing hydraulic motor 5; an inverter 19 that controls operation of the swing electric motor 6; and a controller 21 that outputs to the inverter 19 a torque command value for controlling electric driving torque or electricity generating torque of the swing electric motor 6.

Abstract: A hybrid work machine that can suppress excessive limiting on pump absorption power even in a situation in which supply of electric power to an electric motor is limited is provided. The hybrid work machine includes: an engine 22; an assist generator motor 23 connected to the engine 22 in such a manner that a torque can be transmitted to the engine 22; an electric storage device 24 that supplies electric power to the assist generator motor 23; a monitoring device 28 that monitors the electric storage device 24 and that acquires electric storage device information; a hydraulic pump 41 driven by the engine 22 and the assist generator motor 23; and a pump regulator 43 that regulates a delivery flow rate of the hydraulic pump 41.

Abstract: A hybrid work machine includes a controller and a temperature sensor that detects an electric storage device temperature. In a case where (Tp+Tc)?Te_min, the controller carries out a first comparison in which the controller compares a value of [(Tp+Tc)?Te_min] with a value of Ta_SOC, and the controller then selects a lower value of the first comparison. The controller then carries out a second comparison in which the controller compares the selected lower value of the first comparison with a value of [(Tp+Tc)?Te_max)]. The controller then sets a higher value of the second comparison as the torque of the assist motor Ta, wherein Tc is an accessory torque, Ta_SOC is an adjustment assist motor torque based on a current state of charge of the electric storage device, Ta is the torque of the assist motor, and Te_max is an engine maximum torque.

Abstract: A hybrid work machine has an engine, an assist motor, a hydraulic pump which is driven by the total torque of the engine and the assist motor, and an electric storage device which accumulates electric power generated by the assist motor and supplies the electric power when the assist motor performs electric discharge. The continuous electric discharge from the electric storage device due to continuous operation at high load pressure can be suppressed without an operator experiencing an unusual operational characteristic. To this end, a pump flow rate correction control unit judges whether each hydraulic pump is in a high load operation state or not based on the output horsepower and/or the delivery pressure of each hydraulic pump and performs control such that the delivery flow rate gradually decreases when the hydraulic pump is in the high load operation state and this state continues beyond a predetermined time.

Abstract: A hydraulic excavator is equipped with: an arm cylinder driven by a hydraulic working fluid from a hydraulic pump; a meter-out passage through which the hydraulic working fluid discharged from the arm cylinder flows; a control valve controlling the hydraulic fluid flow rate of the meter-out passage; a pressure sensor detecting a load acting on the arm cylinder; a pressure sensor detecting an operation amount of an operation device operating the arm cylinder; and a controller. The controller alternatively selects a normal operation mode in which the opening area of the control valve is controlled based on an actuator load and the operation amount, and a substitution operation mode in which the opening area of the control valve is controlled based on the operation amount. When the substitution operation mode is selected, a delivery flow rate of the hydraulic pump is further increased as compared with the normal operation mode.

Abstract: A hydraulic system for a work machine includes a first hydraulic pump driving a swing hydraulic motor; a second hydraulic pumps driving a boom cylinder; a first pump displacement increase valve controlling a volume of the first hydraulic pump; a swing pilot pressure sensor detecting a swing operation amount; a boom raising pilot pressure sensor detecting a boom raising operation amount; and a controller controlling a control signal to the first pump displacement increase valve on the basis of the swing operation amount and the boom raising operation amount. The controller controls the control signal in such a manner that a delivery rate of the first hydraulic pump becomes higher as the swing operation amount is larger and an increasing rate of the delivery rate of the first hydraulic pump becomes lower as the boom raising operation amount is larger during a swing boom raising operation.

Abstract: Disclosed is a hydraulic control system of a construction machine capable of achieving a reduction in meter-out pressure loss in accordance with variation of a negative load acting on a hydraulic actuator and capable of preventing deterioration in operability even when an abnormal condition arises in a pressure sensor detecting the magnitude of a negative load.

Abstract: Disclosed is a hydraulic drive system capable of improving the fuel efficiency of a work machine by reducing the pressure loss and drag loss of a hydraulic pump. There are provided an electric motor M; a third pump P3 driven by the electric motor; a third pump hydraulic line L3 to which the delivered hydraulic fluid from the third pump is supplied; a third directional control valve V4 provided in the third pump hydraulic line, switch-operated by an arm operation device 19, and controlling the flow rate of the hydraulic fluid supplied to the arm cylinder 8 from the third hydraulic pump; and a controller 18 drive-controlling the electric motor, wherein the controller drives the third pump by the electric motor when a swing/arm combined operation is detected by pilot pressure sensors S6, S7, S10, S11.