A control device of a work vehicle includes a required output torque determination unit that determines a required output torque of the power transmission device based on an operation amount of the operation device and a traveling speed of the work vehicle, a traveling load estimation unit that estimates a traveling load torque related to a traveling load on the work vehicle, a required output torque correction unit that corrects the required output torque such that the required output torque is included in an allowable output torque range including an estimated traveling load torque, and a drive source control unit that outputs a control signal for the drive source based on a corrected required output torque.

An excavator may include a lower traveling body; an upper turning body pivotally installed to the lower traveling body; an engine installed in the upper turning body; a main pump driven by the engine; and a processor and a memory that stores program instructions causing the processor to control a flow rate of hydraulic oil discharged by the main pump. The program instructions can cause the processor to, when a load of the engine increases, delay a response of the main pump 14 until an actual torque of the engine rises up to a level corresponding to the load of the engine.

A hydraulic system for a work machine includes a travel hydraulic device which changes a travel speed in accordance with switching positions of a hydraulic switch valve. A controller controls a proportional valve so as to change a pressure of an operation fluid at an increasing rate over a time while the hydraulic switch valve is switched from a first switching position to a second switching position to increase the travel speed from a first speed to a second speed, and at a decreasing rate over the time while the hydraulic switch valve is switched from the second switching position to the first switching position to decrease the travel speed from the second speed to the first speed. A magnitude of the increasing rate is different from one of the decreasing rate to output an operation fluid.

Provided is a hydraulic excavator (1) that performs work by operating an arm (9) after moving a bucket (10) to a work start position. An operation determination section (81c) determines, based on an operation performed on an operation device, whether a front work device (1A) is engaged in a work preparation operation for moving the bucket to the work start position. When the operation determination section determines that the front work device is engaged in the work preparation operation at the time of operation of the operation device, an actuator control section (81) controls a bucket cylinder (7) such that the angle of a work tool with respect to a target surface coincides with a preset target angle (θTGT).

It is an object of the present invention to provide a construction machine having a good engine starting property in a low temperature environment. The construction machine of the present invention includes: an electric pump having a delivery port connected to a line part of a pilot line, the line part connecting a pilot pump with a pilot control valve; a motor that drives the electric pump; and a temperature sensor that measures a temperature of a hydraulic working fluid delivered from the pilot pump. A controller starts driving of the motor in the case where a key switch is operated from a key OFF state to a key ON state and where the temperature of the hydraulic working fluid measured by the temperature sensor is lower than a predetermined temperature.

The object of the invention of the present application resides in provision of a work machine that can be improved in operability at start of an action of a hydraulic actuator in a fine operation in which an operation lever is operated by a small amount. To this end, on the basis of a signal from a first timing sensor and a signal from a second timing sensor, a machine body controller controls, before the first timing is sensed, the pump delivery flow rate to a minimum delivery flow rate, controls, after the first timing is sensed but before the second timing is sensed, the pump delivery flow rate to a predetermined delivery flow rate that is greater than the minimum delivery flow rate, and controls, after the second timing is sensed, the pump delivery flow rate to a delivery flow rate according to an operation amount of the operation lever.

Provided is a work machine capable of achieving both low fuel consumption and ensuring of workability. The work machine is configured to, in a state where an output of an engine or hydraulic pump has increased to an increase threshold (S12: Yes) with the rotational speed being at a first rotational speed (S11: Yes), raise the rotational speed from the first rotational speed to a second rotational speed (S13); in a process of raising the rotational speed to the second rotational speed, output, to a regulator, a signal instructing reduction in the discharge rate (S14) so as to keep the output of the engine or hydraulic pump constant; and after the rotational speed has reached the second rotational speed, output, to the regulator, a signal instructing increase in the discharge rate (S16) so as to make the output of the engine or hydraulic pump have a value corresponding to a request load.

A working machine includes a prime mover, a traveling pump driven by a power of the prime mover to deliver operation fluid, a traveling motor rotated by the operation fluid delivered from the traveling pump to have a rotation speed stage shiftable between a first speed stage and a second speed stage higher than the first speed stage, a traveling switching valve shiftable between a first state where the rotation speed stage of the traveling motor is set to the first speed stage and a second state where the rotation speed stage of the traveling motor is set to the second speed stage, an actuation valve configured to change a pilot pressure of a pilot fluid to control a flow of operation fluid delivered from the traveling pump, and a controller configured to control the pilot pressure of the pilot fluid output from the actuation valve so that a value of the pilot pressure differs depending on whether the set rotation speed stage of the traveling motor is the first speed stage or the second speed stage.

A working machine includes a machine body, a traveling device, a traveling motor configured to provide power to the traveling device and to be switched between a first speed and a second speed higher than the first speed, a traveling operation member, an operation detector to detect an operation extent of the traveling operation member, a traveling pump driven in response to the operation extent, a revolution detector to detect a motor revolving speed of the traveling motor, and a controller configured, with the traveling operation member maintained at a predetermined operation extent, to switch the traveling motor from the second speed to the first speed when the motor revolving speed is equal to or less than a deceleration threshold which is less than a first top or maximum revolving speed of the traveling motor switched to the first speed, for the predetermined operation extent.

A power mode recommendation system for a construction machine including a hydraulic system driven by working fluid supplied by a hydraulic pump. A controller configured to analyze engine torque, flow rates of working fluid in use, amounts of fuel consumption of the plurality of power modes and to recommend a power mode indicating lowest fuel consumption, from among the plurality of power modes, using the analysis. A human-machine interface (HMI) device displays the power mode recommended by the controller to an operator. The system recommends an efficiency power mode to an operator by analyzing not only the amount of fuel consumed by the construction machine, but also flow rates of working fluid in use and operating speeds.