A work vehicle includes a steering wheel, a steering cylinder, a steering valve, a feed line, a return line, an electromagnetic valve, and a controller. The steering valve is configured to supply hydraulic fluid to the steering cylinder in response to steering of the steering wheel. The feed line is configured to feed the hydraulic fluid from the steering valve to the steering cylinder. The return line is configured to return the hydraulic fluid from the steering cylinder to the steering valve. The electromagnetic valve is disposed between the feed line and the return line. The controller opens the electromagnetic valve in response to an oil pressure in the feed line.

An electric work vehicle a pump configured to supply hydraulic fluid to a component of the electric work vehicle. Moreover, the electric work vehicle includes a sensor configured to capture data indicative of a pressure of the hydraulic fluid and a controller communicatively coupled to the sensor. As such, the controller is configured to monitor the pressure of the hydraulic fluid relative to a predetermined threshold pressure value based on the data captured the sensor. In addition, the controller is configured to control the operation of the pump such that the pump is switched from a first operating speed range to a second operating speed range when the monitored pressure of the hydraulic fluid falls below the predetermined threshold pressure value.

A shovel includes a lower traveling body, an upper turning body mounted on the lower traveling body, an excavation attachment attached to the upper turning body, a posture detecting device configured to detect the posture of the excavation attachment, an instability detecting device configured to detect information on the instability of the upper turning body due to an excavation load, and a processor configured to correct the posture of the excavation attachment. The processor is configured to open an arm or a bucket of the excavation attachment in response to determining, based on the outputs of the posture detecting device and the instability detecting device, that the excavation load during deep excavation is more than or equal to a predetermined value.

An object of the present invention is to provide a construction machine that is equipped with a pressure accumulating device, which accumulates the return oil of an actuator, and that is capable of adjusting the operation speed of the actuator according to the revolution speed of a prime mover. For this purpose, in a construction machine including a prime mover, a revolution speed setting device that sets a revolution speed of the prime mover, an actuator, a pressure accumulating device that can supply and discharge a hydraulic fluid to and from the actuator, a first control valve disposed on a hydraulic fluid line that connects the pressure accumulating device and the actuator to each other, an operation device that gives an instruction for operation of the actuator, and a controller that is inputted with an operation signal of the operation device and outputs a control signal to the first control valve, the controller controls the first control valve according to an operation amount of the operation device and the revolution speed set by the revolution speed setting device.

A working control device comprises an operation lever for making a boom cylinder (36), an arm cylinder (37) and others work to drive a shovel apparatus (30), and a delivered oil amount control device (a controller (150)). A working oil supply source includes a first electric motor (M1) and a first hydraulic pump (P1). When the operation lever is subjected to a single operation, a number of the motor revolution based on the lever operation is set to control the first electric motor. When the number of motor revolution is less than a necessary minimum number of revolutions, the necessary minimum number is set to control the first electric motor (M1). When the operation lever is subjected to a composite operation, a total number of motor revolutions based on the lever operations is set. When the total number is less than a necessary minimum number of revolutions, the necessary minimum number is set to control the first electric motor (M1).

Provided is a work machine capable of eliminating the inconvenience from the operator of the work machine as much as possible while deterring a contact between the work machine and workers, and suppressing a decrease in productivity of the work machine. A work machine 5 includes: an identification information recognition device 41 configured to recognize identification information on a person who enters a predetermined region R around the work machine 5; and a controller 7 configured to control the work machine in accordance with the identification information. When a person enters the predetermined region R under the condition that the work machine 5 is ready for operation, the controller 7 counts the number of times the person enters the predetermined region R as the number of approaches for each person distinguished with the identification information, and controls the work machine 5 based on the counted number of approaches in accordance with the identification information of the person who is in the predetermined region R.

Both a control for limiting operation of a machine body and a control for raising engine speed are achieved when an obstacle is detected. To this end, a machine controller performs operation limiting control by conducting a control for reducing the speed of the engine when the machine body does not require engine speed increase control and an obstacle is sensed by obstacle sensors, and the machine controller performs supply flow rate reduction control for reducing the flow rates of the hydraulic fluid supplied to hydraulic actuators from a hydraulic pump when the machine body requires the engine speed increase control and an obstacle is sensed by the obstacle sensors.

An excavator includes a lower traveling body; an upper turning body turnably mounted to the lower traveling body; an attachment that is attached to the upper turning body; and a power engine that is mounted to the upper turning body. The excavator is configured such that, before a low-load operation by the attachment is started, a rotation speed of the power engine is reduced.

The present invention provides a construction machine equipped with a pressure accumulation device that accumulates return oil from an actuator, and that can implement both improvement in fuel efficiency with enhancement in workability. To achieve the foregoing, a controller sets an actuator upper limit output power that is an upper limit for an output power of the actuator according to a work mode selected by a work mode selection device, and controls a first control valve and a second control valve such that a sum of an output power of a hydraulic pump and an output power of the pressure accumulation device does not exceed the actuator upper limit output power.

A hydraulic excavator includes a traveling body, a slewing body, a working front having a boom, an arm, and a bucket, an operation amount detector, a posture detector, a load detector, a drive controller, and a drive unit. The drive controller calculates a target operation speed of the actuator based on the operation amount, the posture of the working front, and the target surface distance so that the bucket excavates along the construction target surface, and determines soil hardness of a place to be excavated based on a result detected by the load detector, corrects the target operation speed based on the soil hardness, and generates a motion command value. The drive controller determines a target jack-up speed when the hydraulic excavator jacks up based on the target surface distance, and corrects the target operation speed based on the determined target jack-up speed.