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 working machine includes a prime mover, a hydraulic pump driven by power of the prime mover, a cooler including a cooling fan rotated by either the power of the prime mover or hydraulic fluid delivered from the hydraulic pump, and a controller configured or programmed to perform a reduction control for reducing a target fan rotation speed that is a target rotation speed of the cooling fan in response to reduction of an actual prime mover rotation speed that is an actual rotation speed of the prime mover, and to perform, after the reduction control, a restoration control for restoring the target fan rotation speed. The controller is configured or programmed to make a difference between a reduction rate of the target fan rotation speed in the reduction control and an increase rate of the target fan rotation speed in the restoration control.

Problem to be solved: To provide a hydraulic circuit for the construction machine which enables to use the relief valve of low capacity in the work tool circuit. Solution: The hydraulic circuit 2 for a construction machine has: a hydraulic pump 4 of variable capacity, a work tool 6 operated by hydraulic oil delivered by the hydraulic pump 4, a work tool operating device 10 to output a signal for operating the work tool 6, a control valve 14 allowing the hydraulic pump 4 to supply the hydraulic oil to the work tool 6 based on the signal output from the work tool operating device 10, a tool's relief valve 44 to release the hydraulic oil flowing between the control valve 14 and the work tool 6, a pressure sensor 46 to detect a pressure of hydraulic oil flowing into the work tool 6, and a controller 48 to reduce a delivery rate from the hydraulic pump 4 when the pressure detected by the pressure sensor 46 exceeds a predetermined value.

A portable hydraulic power unit includes a frame, a fluid tank supported by the frame, and a manifold supported by the frame. The fluid tank is configured to store a supply of hydraulic fluid for powering a hydraulically-driven tool. A reciprocating pump is mounted on the exterior of the fluid tank and on the exterior of the manifold. The reciprocating pump is secured to the fluid tank and the manifold with fasteners extending through a cylinder body of the reciprocating pump.

A fluid control valve can suppress heat generation when discharging charges from a piezo actuator for contraction and reduce energy necessary to drive the piezo actuator. The fluid control valve includes a piezo actuator and a drive circuit connected to the piezo actuator is adapted so that the drive circuit includes: a flyback transformer including a primary side coil connected to a DC power supply DV and a secondary side coil connected to the piezo actuator; a charge switch that is connected to the primary side coil and switched from on to off when the piezo actuator charges; a discharge switch that is connected to the secondary side coil and switched from off to on when the piezo actuator discharges; and a regenerative capacitor that is connected to the primary side coil and into which electric energy due to the discharge of the piezo actuator is regenerated.

A fluid heating system for an electric work machine powered by a battery may include a fluid heater arranged and configured to heat fluid on the work machine and a control module configured to control fluid heating operations by controlling power to the fluid heater based on active operation of a battery charging unit.

The hydraulic system according to the invention comprises a hydraulic circuit with a low-pressure region and a high-pressure region; a volume- and/or speed-variable hydraulic machine, which is driven by a first electric motor and has an inlet and an outlet and provides a volume flow of a hydraulic fluid in the high-pressure region of the hydraulic circuit. The hydraulic system according to the invention further comprises at least one movable shaft, which is arranged in the high-pressure region of the hydraulic circuit; at least one valve, which separates the high-pressure region from the low-pressure region; and at least one hydraulic fluid container, which is hydraulically connected to the low-pressure region of the hydraulic circuit. The hydraulic system according to the invention also has a discharge line, which discharges hydraulic fluid from the leakage of the hydraulic machine, and a cooling line for transporting the hydraulic fluid in order to cool the electric motor, the discharge line and the cooling line being fluidically connected to at least one of the hydraulic fluid containers.

An electric work vehicle includes a hydraulic actuator and a pump configured to supply hydraulic fluid to the hydraulic actuator, with the pump being operable within an operating speed range extending between a minimum operating speed value and a maximum operating speed value. Furthermore, the electric work vehicle includes a sensor configured to capture data indicative of a temperature of the hydraulic fluid and a controller communicatively coupled to the sensor. As such, the controller is configured to monitor the temperature of the hydraulic fluid relative to a predetermined minimum fluid temperature as the pump is operating within the operating speed range. In addition, the controller is configured to adjust the operating speed range of the pump by increasing at least one of the minimum operating speed value or the maximum operating speed value when the monitored temperature of the hydraulic fluid falls below the predetermined minimum fluid temperature.

Provided is an electrohydrostatic actuation system including an emergency shut-off circuit to be actuated stably with a simple configuration. The electrohydrostatic actuation system includes: a hydraulic cylinder (24) including a piston (25) to which a valve element is connected, a first chamber (24A), and a second chamber (24B); a hydraulic pump (21) configured to supply hydraulic fluid to the first chamber (24A) or the second chamber (24B); a servo motor (M) configured to drive the hydraulic pump (21); a shuttle valve (11) configured to establish communication to a downstream side under a state in which a hydraulic pressure generated by the hydraulic pump (21) is maintained; a solenoid valve (12) configured to receive the hydraulic pressure via the shuttle valve (11) as a pilot pressure; and a logic valve (13) including a first port configured to receive the pilot pressure from the solenoid valve (12), and a second port to be communicated to the first chamber (24A) of the hydraulic cylinder (24). When the solenoid valve (12) is brought to a de-energized state, the pilot pressure of the logic valve (13) is released, and the logic valve (13) causes the hydraulic fluid in the first chamber (24A) communicated to the second port to flow into the second chamber (24B) so that emergency shut-off of the valve element is achieved by a return spring (26).

A working machine includes a prime mover, a hydraulic pump driven by power of the prime mover, a cooler including a cooling fan rotated by either the power of the prime mover or hydraulic fluid delivered from the hydraulic pump, and a controller configured or programmed to perform a reduction control for reducing a target fan rotation speed that is a target rotation speed of the cooling fan in response to reduction of an actual prime mover rotation speed that is an actual rotation speed of the prime mover, and to perform, after the reduction control, a restoration control for restoring the target fan rotation speed. The controller is configured or programmed to make a difference between a reduction rate of the target fan rotation speed in the reduction control and an increase rate of the target fan rotation speed in the restoration control.