A work vehicle includes a first hydraulic pump that supplies hydraulic oil to a first hydraulic motor so as to drive a first travel device forward when hydraulic pressure applied to a first port is higher than hydraulic pressure applied to a second port, and a second hydraulic pump to drive a second travel device forward when hydraulic pressure applied to a third port is higher than hydraulic pressure applied to a fourth port. A first pilot oil passage, a second pilot oil passage, a third pilot oil passage, and a fourth pilot oil passage connect the operation device to first, second, third, and fourth ports, respectively. A first bypass oil passage connects the first pilot oil passage and the fourth pilot oil passage. A second bypass oil passage connects the second pilot oil passage and the third pilot oil passage. A first throttle is provided in the first bypass oil passage. A second throttle is provided in the second bypass oil passage.

Systems and methods are disclosed herein for fluid temperature-dependent control of engine speeds in a self-propelled work vehicle. An engine speed sensor generates signals representing an engine speed, and a temperature sensor generates signals representing a hydraulic fluid temperature. A controller receives the respective signals from the engine speed sensor and the temperature sensor. The controller is further configured, responsive to a startup command, to generate output signals preventing an increase in the engine speed to a target engine speed at least while the temperature of the hydraulic fluid is in a first temperature state. The controller may, e.g., automatically generate output signals for continuous and/or stepwise transitioning of the engine speed to the target engine speed, in accordance with a monitored temperature of the hydraulic fluid and corresponding temperature states.

A hydraulic system for a work vehicle that has a frame, a ground-engaging implement that moves the frame over a ground surface, and an attachment connected to the frame for movement with respect to the frame. The hydraulic system includes a pump that pumps hydraulic fluid, a first conduit fluidly connecting the pump and the attachment, a reservoir that contains hydraulic fluid, a second conduit fluidly connecting the pump to the reservoir, a fluid resistor fluidly connected with the second conduit, and a valve. The fluid resistor dissipates power from the work vehicle. The valve actuates between a first state in which the valve fluidly connects the pump to the first conduit such that hydraulic fluid is directed to the attachment, and a second state in which the valve fluidly connects the pump to the second conduit such that fluid is directed through the fluid resistor and into the reservoir.

A mobile machine control method includes receiving, by a single controller, a first request for movement of the machine by a ground-engaging device, receiving, by the single controller, a second request for movement of an implement system of the machine, and determining, with the single controller, an amount of desired power from an engine to satisfy the first request and the second request. The method also includes selecting an engine speed from a plurality of candidate engine speeds to produce the desired power and operating the engine at the selected engine speed to produce the desired power.

A working machine includes a switching valve to switch between a first state and a second state, the first state allowing a revolving speed of a traveling motor to be a first speed, the second state allowing the revolving speed of the traveling motor to be a second speed, and a controller device to reduce the revolving speed of the prime mover in either acceleration to switch from the first state to the second state or deceleration to switch from the second state to the first state. The controller device associates a return timing with a switch timing in either the acceleration or deceleration, the return timing allowing an actual revolving speed of a prime mover to start returning toward a first target revolving speed after the actual revolving speed is reduced, the switch timing allowing the switching valve to switch to either an acceleration side or a deceleration side.

In a hydraulic drive system used for an electrically driven hydraulic work machine that drives a hydraulic pump by an electric motor and supplies a hydraulic fluid to plural actuators to carry out work, the power consumption of the hydraulic pump is kept from exceeding a value decided in advance. For this purpose, a controller calculates target power to be consumed by the hydraulic pump on the basis of the capacity of the hydraulic pump, the delivery pressure of the hydraulic pump sensed by a pressure sensor, and a target revolution speed of the electric motor, and limits the target revolution speed of the electric motor in such a manner that the target power falls within a range of the maximum allowable power.

It is made possible to perform power reduction control during non-operation of control levers, and suppress power consumption of a power source when a control lever is moved by an erroneous operation, and thus reduce energy consumption. Accordingly, a controller 50 performs the power reduction control when a non-operation time exceeds a set time after a transition is made from a state in which at least one control lever is operated to a non-operation state in which none of the control levers is operated, and the controller 50 cancels the power reduction control when at least one control lever is operated in a state in which the power reduction control is performed. In addition, the set time is set as a first set time Tth1 when an operation time until at least one of levers 14 and 34 makes a transition to the non-operation state is longer than a monitoring time Tth0, and the set time is set as a second set time Tth2 shorter than the first set time Tth1 when the operation time until the at least one control lever makes a transition to the non-operation state is shorter than the monitoring time Tth0.

The present invention relates to a mobile work machine, in particular a hydraulic excavator, which comprises an engine for driving the mobile work machine, a hydraulic power generation unit which is coupled to the engine and is designed to convey a hydraulic volume in a manner which is dependent on a rotational speed of the engine, and a plurality of hydraulic elements which can be actuated by way of the conveyed volume of the hydraulic power generation unit and are assigned to various functions of the mobile work machine. The machine is characterized by a control unit for detecting a defined operating mode of the mobile work machine, wherein the control unit is designed to set the setpoint rotational speed of the engine in a manner which is dependent on the detected defined operating mode.

A work vehicle control system includes: a hydraulic device configured to adjust a supply state of hydraulic fluid supplied to a hydraulic cylinder configured to cause a work tool to operate; and a control device configured to control the hydraulic device. The control device includes: an operation data acquisition unit configured to acquire operation data indicating an operation state of an operating device operated in order to cause a work tool to perform dumping and tilting movements; and a control command unit configured to output, based on the operation data, a control command to control the hydraulic device; an operating condition determination unit configured to determine, based on the operation data, whether the operating device is operated under prescribed operating conditions; and a limit command unit configured to output a limit command to limit the control command when the operating device is determined to be operated under the operating conditions.

A work machine includes an engine, a travel drive system, a work implement, an apparatus drive system with a hydraulic pump, an accelerator operating member, a work implement operating member, and a controller. The controller controls the apparatus drive system in accordance with an operating amount of the work implement operating member. The controller determines a target tractive force of the travel drive system based on an operating amount of the accelerator operating member. The controller determines an allowable acceleration of the work machine. The controller determines an upper limit of tractive force of the travel drive system based on the allowable acceleration. The controller corrects the target tractive force so as to be equal to or less than the upper limit when the target tractive force is greater than the upper limit. The controller controls the travel drive system based on the corrected target tractive force.