A shovel includes a traveling body, an upper turning body turnably provided on the traveling body, an attachment including a boom, an arm, and a bucket and attached to the upper turning body, and a processor. The processor is configured to correct the motion of the attachment in such a manner as to control a slip of the traveling body toward the back in the extension direction of the attachment.

To provide a hydraulic drive system for a work machine capable of securing a favorable operability in the case where hydraulic fluid discharged from a hydraulic actuator is regenerated for driving other hydraulic actuator. The hydraulic drive system for a work machine includes: a regeneration line that connects a bottom-side hydraulic chamber of a hydraulic cylinder to a portion between a hydraulic pump and a second hydraulic actuator; a regeneration flow rate adjustment device that supplies at least part of the hydraulic fluid discharged from the bottom-side hydraulic chamber to a portion between the hydraulic pump and the second hydraulic actuator through the regeneration line; a differential pressure calculating section that reads a pressure in the bottom-side hydraulic chamber of the hydraulic cylinder detected by a first pressure sensor and a pressure between the hydraulic pump and the second hydraulic actuator detected by a second pressure sensor, and calculates a differential pressure, or a differential pressure sensor; and a control unit that controls the regeneration flow rate adjustment device such as to gradually increase the flow rate of the hydraulic fluid flowing through the regeneration line according to an increase in the differential pressure calculated by the differential pressure calculation section or in the differential pressure detected by the differential pressure sensor.

A regeneration control hydraulic system for an excavator, including at least one hydraulic pump, an actuator, a regeneration oil path, and a regeneration cut-off oil path. The regeneration oil path is configured to send a return oil as a regeneration oil to a cavity having a negative pressure of the actuator. The regeneration oil path is provided with a regeneration valve and a first control valve. The first control valve is configured to control the regeneration oil to enter the cavity having the negative pressure of the actuator when a working device of the excavator retracts inwards, or to control the oil to be discharged from the actuator to the regeneration cut-off oil path when the working device swings outwards. The regeneration cut-off oil path is configured to send the regeneration oil passing through the regeneration valve or the oil discharged from the actuator to other destinations.

An area limiting excavation control system for construction machines including a control unit (9) that performs area limiting control by controlling at least one of a plurality of hydraulic cylinders (3a, 3b, 3c) on the basis of a posture and a position of each of a boom (1a), an arm (1b), and a bucket (1c). The control system includes an angle sensor group (8) that detects rotational angles of the boom (1a), the arm (1b), and the bucket (1c), and a tilting angle sensor group (81) that detects ground angles of the boom (1a), the arm (1b), and the bucket (1c). The control unit (9) selects, from among the angle sensor group (8) and the tilting angle sensor group (81), a sensor to be used for calculating a posture and a position of each of the boom (1a), the arm (1b), and the bucket (1c) in accordance with a magnitude of speed of at least one of the boom (1a), the arm (1b), and the bucket (1c).

A walking excavator (1) having a superstructure (2) and an undercarriage (29), and a cab (3) disposed on the superstructure (2), and four walking legs (4) pivotably disposed on the undercarriage (29), and an excavator arm (5) which is pivotably mounted on the superstructure (2) and to which an excavating tool (6), in particular an excavator bucket, is fastened or able to be fastened. A dual-action differential cylinder (7) pivots the excavator arm (5) up and down relative to the superstructure (2) and is articulated on the superstructure (2), on one side, and on the excavator arm (5), on an other side. For applying additional force along with the dual-action differential cylinder (7) when pivoting the excavator arm (5) down relative to the superstructure (2), a single-action differential cylinder (8) is additionally articulated on the superstructure (2), on one side, and on the excavator arm (5), on an other side.

A shovel includes a lower traveling body, an upper turning body turnably mounted on the lower traveling body, an engine provided in the upper turning body, a hydraulic pump and a hydraulic oil tank provided in the upper turning body, a plurality of hydraulic actuators driven by the hydraulic pump, and a hydraulic circuit connected to the hydraulic pump, wherein the hydraulic circuit includes a plurality of control valves configured to control flows of hydraulic oil between the hydraulic pump and the plurality of hydraulic actuators, and a unified bleed-off valve configured to collectively control bleed-off flowrates of the plurality of control valves, wherein the hydraulic circuit is configured so that a discharge pressure of the hydraulic pump becomes equal to or less than a predetermined pressure during start-up of the engine.

A hydraulic control system is disclosed for an excavation machine including a tool linkage system. The hydraulic control system may have a first actuator configured to move a first link of the tool linkage system in response to input from an operator of the excavation machine, and a pressure sensor configured to generate a signal indicative of a pressure of the first actuator. The hydraulic control system may also have a second actuator configured to move a second link of the tool linkage system in response to input from the operator. In addition, the hydraulic control system may have a controller in communication with the pressure sensor, the first actuator, and the second actuator. The controller may be configured to automatically affect operation of the first actuator based on the pressure signal at times when movement of the second actuator is being requested by the operator and movement of the first actuator is being requested by the operator at a level less than a threshold.

An electricity storage device (20) includes voltage detectors (25A) to (25C) detecting cell voltages (VcA) to (VcC) and a controller (26) controlling the cell voltages (VcA) to (VcC). The controller (26) includes a balancing control section (27) performing balancing control reducing deviations of the cell voltages (VcA) to (VcC), a maximum cell voltage calculating section (28) calculating a maximum cell voltage (Vmax) in the cell voltages (VcA) to (VcC), a minimum cell voltage calculating section (29) calculating a minimum cell voltage (Vmin) in the cell voltages (VcA) to (VcC), and an abnormality detecting section (34) detecting an abnormality of the electricity storage device (20) in accordance with whether or not a differential voltage (ΔV) between the maximum cell voltage (Vmax) and the minimum cell voltage (Vmin) is within a range of a reference differential voltage (ΔVstd1) calculated based on a history of the balancing control performed.

A regeneration control hydraulic system for an excavator, including at least one hydraulic pump, an actuator, a regeneration oil path, and a regeneration cut-off oil path. The regeneration oil path is configured to send a return oil as a regeneration oil to a cavity having a negative pressure of the actuator. The regeneration oil path is provided with a regeneration valve and a first control valve. The first control valve is configured to control the regeneration oil to enter the cavity having the negative pressure of the actuator when a working device of the excavator retracts inwards, or to control the oil to be discharged from the actuator to the regeneration cut-off oil path when the working device swings outwards. The regeneration cut-off oil path is configured to send the regeneration oil passing through the regeneration valve or the oil discharged from the actuator to other destinations.

A shovel includes a lower traveling structure, an upper swing structure swingably mounted on the lower traveling structure, an engine mounted on the upper swing structure, a hydraulic pump configured to be driven by the engine, and processing circuitry configured to determine a command value by energy saving control and to control a flow rate of hydraulic oil discharged by the hydraulic pump according to the command value. The processing circuitry is configured to control the command value.