A hydraulic system includes a hydraulic pump, a first hydraulic actuator, a second hydraulic actuator, a first control valve to control the first hydraulic actuator, a second control valve connected to a downstream side of the first control valve and configured to control the second hydraulic actuator, a return fluid tube in which return fluid discharged from the first hydraulic actuator flows, the return fluid tube coupling the first control valve and the first hydraulic actuator, an internal fluid tube arranged in the first control valve and connected to the return fluid tube, an external fluid tube connected to the internal fluid tube, the external fluid tube coupling the first control valve and the second control valve, a branched fluid tube branched from the external fluid tube and connected to a discharge fluid tube, and a pressurizing portion provided to the discharge fluid tube.

Provided is a work machine which can increase the operation speed of an actuator by a regeneration function while securing the position control accuracy of the actuator. A controller is configured to calculate a regeneration flow rate on the basis of an input amount of an operation lever and a target actuator flow rate, subtract the regeneration flow rate from the target actuator flow rate to calculate a target actuator supply flow rate, calculate a target flow rate control valve opening amount on the basis of the target actuator supply flow rate, calculate a target pump flow rate that is equal to or higher than a total target actuator supply flow rate, control a selector valve on the basis of the input amount of the operation lever, control a flow rate control valve according to the target flow rate control valve opening amount, and control a hydraulic pump according to the target pump flow rate.

An excavator includes a control valve configured to control hydraulic oil to be supplied to an actuator, based on pilot pressure; an electric operation device configured to output an operation signal; a gate lock device; a gate lock valve provided on a pilot line supplying the pilot pressure to the control valve, and configured to open or close according to a state of the gate lock device, so as to switch between a locked state and a released state; a proportional valve provided on the pilot line; and a control part configured to receive as input the operation signal, to control the proportional valve, wherein the control part determines, in a case where the gate lock valve is in the locked state by the gate lock device and an operation is performed on the electric operation device, the operation as an operational error.

A main controller generates a supplemented design face that passes through a junction or above the junction between a first design face and a second design face adjacent to each other, among a plurality of design faces, the supplemented design face having one end thereof positioned on the first design face and another end thereof positioned on the second design face, sets a curvature 1/R of the supplemented design face according to an arm operation amount of an operation lever device, and executes semi-automatic excavation control to control a boom cylinder with one of the faces included in the supplemented design face being set as the target face.

A work machine includes a lower structure, a slewing upper structure attached to the lower structure via a slewing mechanism, an attachment, including at least a boom, and attached to the slewing upper structure, a boom cylinder configured to drive the boom, a work tool attached to the attachment, and a controller. The controller includes a weight calculating part configured to measure a weight of a transporting object to be transported by the work tool, based on a boom cylinder pressure of the boom cylinder, and a vibration control part configured to generate a command for reducing vibration of the attachment.

Provided is a work machine which can achieve both of excellent operability when an operator manually operates a machine body or a work device and an accuracy of control of the machine body or the work device when a controller performs automatic control. The controller is configured to, in a case where the automatic control function selector switch gives an instruction to disable the automatic control function, adjust an opening amount of a bleed-off valve to a maximum opening amount or an opening amount corresponding to input amounts of control levers, and in a case where the automatic control function selector switch gives the instruction to enable the automatic control function, adjust the opening amount of the bleed-off valve, in at least part of an operation region of the control levers, so as to be smaller than the opening amount with the instruction to disable the automatic control function being given.

A work vehicle provided with a loading hydraulic circuit (A), including at least a main hydraulic pump (31), a lift arm cylinder (8) and a control valve (32), an auxiliary hydraulic pump (31), a negative parking brake device (PB), and a parking brake releasing hydraulic circuit (B2), in which the vehicle includes: a loading operation hydraulic circuit (B1) located upstream of the parking brake releasing hydraulic circuit; an emergency flow path (80) for supplying the pressure oil discharged from the auxiliary hydraulic pump to the parking brake device through the loading operation hydraulic circuit in an emergency; and a valve unit (81) located in the emergency flow path. If the pressure of the parking brake releasing hydraulic circuit is lower than the brake release pressure to release the braking state of the parking brake device, the valve unit is switched to the communicating position.

There is provided a work machine that is capable of realizing operability and energy saving ability that are equivalent to those of work machines that have a joint line to be used during swinging/boom raising operation, without incorporating a joint line for supplying a pressurized fluid from a second pump to a bottom-side chamber of a boom cylinder. The controller is configured to compute a hypothetical flow rate representing a flow rate in a hypothetical joint line, compute a first pump provisional target flow rate on the basis of an operation amount of a boom operation device, compute a second pump provisional target flow rate on the basis of an operation amount of a swing operation device, compute a first pump final target flow rate by adding the hypothetical flow rate to the first pump provisional target flow rate, and compute a second pump final target flow rate by subtracting the hypothetical flow rate from the second pump provisional target flow rate.

A shovel includes a lower traveling structure, an upper swing structure mounted on the lower traveling structure, an engine mounted on the upper swing structure, a hydraulic pump configured to be driven by the engine, a hydraulic actuator, an operating device configured to operate the hydraulic actuator, and a hardware processor configured to control the discharge quantity of the hydraulic pump through negative control and change a control characteristic of the negative control according to the details of an operation on the operating device.

A work machine includes a flow control valve that controls a flow rate of a hydraulic fluid supplied to a hydraulic actuator, a center bypass line that introduces the hydraulic fluid from a pump through a center bypass passage section of the flow control valve into the tank, a bypass cutoff valve that controls an opening of the center bypass line, a solenoid proportional valve that generates a pilot pressure for controlling the bypass cutoff valve, a pilot valve that generates a pilot pressure for controlling the flow control valve on the basis of an amount of operation of an operation device, and a controller that controls the solenoid proportional valve on the basis of the amount of operation. The controller controls the solenoid proportional valve to reduce an opening area of the bypass cutoff valve according to an increase in the amount of operation in a case the amount of operation is less than a predetermined amount of operation, and controls the solenoid proportional valve to make the opening area of the bypass cutoff valve larger than the minimum opening area in a case the amount of operation is a maximum amount of operation.