Abstract: A shovel includes a lower traveling body, an upper rotating body, an attachment including a boom and an arm, a controller, an engine, and a hydraulic pump that is driven by the engine and discharges hydraulic oil to drive the attachment. The controller is configured to obtain a hydraulic load applied to the attachment and calculate an engine speed command at predetermined time intervals based on the obtained hydraulic load.

Abstract: A shovel may has a first pump that discharges a first hydraulic oil, a second pump that discharges a second hydraulic oil, a pump/motor that discharges a third hydraulic oil, an arm cylinder that at least the first hydraulic oil can flow into, and a boom cylinder that at least the second hydraulic oil can flow into. When the arm cylinder and the boom cylinder operate simultaneously, the arm cylinder is actuated by the first hydraulic oil or the third hydraulic oil, and the boom cylinder is actuated by the second hydraulic oil.

Abstract: A shovel is disclosed, which includes a lower traveling body; an upper rotating body mounted on the lower traveling body; an engine mounted on the upper rotating body; a hydraulic pump of a variable volume type; a hydraulic actuator to which pressurized oil is supplied from the hydraulic pump; a flow rate control valve configured to control, based on operation amount of an operation member, a flow rate of the oil to the hydraulic actuator from the hydraulic pump; and a controller configured to control the hydraulic pump. The controller calculates a virtual bleed flow rate from a bleed opening area of the flow rate control valve, determines a pump demand flow rate based on the calculated virtual bleed flow rate, and performs a virtual bleed-off control such that a discharge flow rate of the hydraulic pump becomes the determined pump demand flow rate.

Abstract: A shovel includes a first pump 14L; a second pump 14R; a hydraulic swing motor 21; a pump/motor 14A configured to generate an engine-assist torque in response to hydraulic oil from the hydraulic swing motor 21 during swing deceleration; an accumulator 80 configured to accumulate the hydraulic oil flowing out of the hydraulic swing motor 21 during swing deceleration; a regeneration valve 22G configured to switch open/close of transfer from a discharge port 21L to the pump/motor 14A and the accumulator 80; and a controller configured to control the regeneration valve 22G. During swing deceleration, the controller adjusts an open area of the regeneration valve 22G in such a way that a swing flowing-out pressure becomes a swing braking target pressure, and causes the hydraulic oil flowing out of the hydraulic swing motor 21 to flow into the pump/motor 14A and the accumulator 80 at the same pressure.

Abstract: A shovel is disclosed, which includes a lower traveling body; an upper rotating body mounted on the lower traveling body; an engine mounted on the upper rotating body; a hydraulic pump of a variable volume type; a hydraulic actuator to which pressurized oil is supplied from the hydraulic pump; a flow rate control valve configured to control, based on operation amount of an operation member, a flow rate of the oil to the hydraulic actuator from the hydraulic pump; and a controller configured to control the hydraulic pump. The controller calculates a virtual bleed flow rate from a bleed opening area of the flow rate control valve, determines a pump demand flow rate based on the calculated virtual bleed flow rate, and performs a virtual bleed-off control such that a discharge flow rate of the hydraulic pump becomes the determined pump demand flow rate.

Abstract: A hydraulic control apparatus is disclosed that controls a hydraulic pump in a construction machine in which a hydraulic actuator is connected to the hydraulic pump via a directional control valve of a closed center type, and in which a position of the directional control valve is changed according to an operation amount of an operation member. The hydraulic control apparatus includes a virtual negative control pressure calculating part configured to calculate, based on the operation amount of the operation member and a discharge pressure of the hydraulic pump, a virtual negative control pressure when a negative control system is assumed; and a part configured to calculate a control command value for the hydraulic pump based on the virtual negative control pressure.

Abstract: A shovel includes a first pump 14L; a second pump 14R; a hydraulic swing motor 21; a pump/motor 14A configured to generate an engine-assist torque in response to hydraulic oil from the hydraulic swing motor 21 during swing deceleration; an accumulator 80 configured to accumulate the hydraulic oil flowing out of the hydraulic swing motor 21 during swing deceleration; a regeneration valve 22G configured to switch open/close of transfer from a discharge port 21L to the pump/motor 14A and the accumulator 80; and a controller configured to control the regeneration valve 22G. During swing deceleration, the controller adjusts an open area of the regeneration valve 22G in such a way that a swing flowing-out pressure becomes a swing braking target pressure, and causes the hydraulic oil flowing out of the hydraulic swing motor 21 to flow into the pump/motor 14A and the accumulator 80 at the same pressure.

Abstract: A hydraulic control apparatus is disclosed which includes an unloading valve controlling part; an command value calculating part configured to calculate, based on an operation amount of an operation member for changing a position of the directional control valve and a discharge pressure of the hydraulic pump, a virtual negative control pressure, and calculates a control command value for the hydraulic pump based on the virtual negative control pressure; and a correcting part configured to operate under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is closed, wherein the correcting part corrects the control command value or a parameter, which is used in calculating the control command value, such that a discharge flow rate of the hydraulic pump is a predetermined flow rate.

Abstract: A shovel includes a lower traveling body, an upper rotating body, an attachment including a boom and an arm, a controller, an engine, and a hydraulic pump that is driven by the engine and discharges hydraulic oil to drive the attachment. The controller is configured to obtain a hydraulic load applied to the attachment and calculate an engine speed command at predetermined time intervals based on the obtained hydraulic load.

Abstract: A shovel may has a first pump that discharges a first hydraulic oil, a second pump that discharges a second hydraulic oil, a pump/motor that discharges a third hydraulic oil, an arm cylinder that at least the first hydraulic oil can flow into, and a boom cylinder that at least the second hydraulic oil can flow into. When the arm cylinder and the boom cylinder operate simultaneously, the arm cylinder is actuated by the first hydraulic oil or the third hydraulic oil, and the boom cylinder is actuated by the second hydraulic oil.

Abstract: A hydraulic control apparatus is disclosed which includes an unloading valve controlling part; an command value calculating part configured to calculate, based on an operation amount of an operation member for changing a position of the directional control valve and a discharge pressure of the hydraulic pump, a virtual negative control pressure, and calculates a control command value for the hydraulic pump based on the virtual negative control pressure; and a correcting part configured to operate under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is closed, wherein the correcting part corrects the control command value or a parameter, which is used in calculating the control command value, such that a discharge flow rate of the hydraulic pump is a predetermined flow rate.

Abstract: A hydraulic control apparatus is disclosed that controls a hydraulic pump in a construction machine in which a hydraulic actuator is connected to the hydraulic pump via a directional control valve of a closed center type, and in which a position of the directional control valve is changed according to an operation amount of an operation member. The hydraulic control apparatus includes a virtual negative control pressure calculating part configured to calculate, based on the operation amount of the operation member and a discharge pressure of the hydraulic pump, a virtual negative control pressure when a negative control system is assumed; and a part configured to calculate a control command value for the hydraulic pump based on the virtual negative control pressure.