An electro-hydraulic circuit includes a supply line that connects between a hydraulic supply device that supplies hydraulic fluid and a driving part to be driven by a hydraulic pressure of the hydraulic fluid; a switching valve disposed in the supply line to switch between switching lines for the hydraulic fluid supplied to the driving part; a pilot hydraulic line connected to the switching valve to supply the hydraulic fluid for switching between the switching lines; a check valve disposed in the pilot hydraulic line; a solenoid valve disposed in the pilot hydraulic line to change a supply state of the hydraulic fluid to the switching valve; a sealing material disposed in the switching valve to seal the hydraulic fluid; and a relief valve disposed in the pilot hydraulic line to release the pilot hydraulic pressure

A switching valve includes a sleeve on which a plurality of ports are disposed; a spool that is disposed inside the sleeve to move in an axial direction by a pilot hydraulic pressure to switch between switching lines each serving as a flow channel for hydraulic fluid that is formed by a combination of the ports; a first energizing unit that energizes the spool against the pilot hydraulic pressure; a relief hole that is disposed on the spool to discharge the hydraulic fluid with the pilot hydraulic pressure; a valve body that closes the relief hole; and a second energizing unit that energizes the valve body toward the relief hole of the spool against the pilot hydraulic pressure, and when the pilot hydraulic pressure exceeds a predetermined value, opens the relief hole.

In a hydraulic system for a working machine, a controller is configured or programmed to increase an output-port pressure of one activation valve for one hydraulic device and an output-port pressure of another activation valve for another hydraulic device to a normal pressure higher than a preloading pressure from a state where the output-port pressure of the one activation valve is equal to the preloading pressure and the output-port pressure of the other activation valve is lower than the preloading pressure, by causing the output-port pressure of the one activation valve to be lower than the preloading pressure and increasing the output-port pressure of the other activation valve to the normal pressure.

To achieve improvement in work efficiency of calibration work and improvement in calibration accuracy, by performing control so that the time taken to increase the sweep of an applied current becomes substantially constant, upon the calibration of a valve opening position current value when a valve operated by electrical current applied to an electrical actuator opens a flow passage. There is provided a predicted value calculating means for predicting a calibration value of a valve opening position current value on the basis of information concerning valve opening position current values, and the sweep starting current value is set so that the time taken to increase the sweep to a predicted value predicted by the predicted value calculating means from a sweep start becomes a fixed time.

A shovel includes a lower traveling body, an upper traveling body turnably mounted on the lower traveling body, a hydraulic actuator, an operating apparatus configured to be operated to operate the hydraulic actuator, an object detector configured to detect an object within a predetermined area around the shovel, a gate lock lever configured to switch the operating apparatus between an enabled state and a disabled state, and a control device. The control device is configured to switch the operating apparatus between the enabled state and the disabled state separately from the gate lock lever, and to disable the operating apparatus in response to determining that the object is present within the predetermined area based on the output of the object detector while the operating apparatus is switched to the enabled state by the gate lock lever, during the standby state of the shovel.

An example valve includes: (i) a valve body comprising a supply port and an operating port; (ii) a sleeve comprising a first opening fluidly coupled to the supply port, a second opening fluidly coupled to the operating port, and a seat; (in) a spool configured to move axially within the sleeve, wherein the spool is configured to he seated on the seat of the sleeve when the valve is unactuated, and wherein when the valve is actuated, the spool moves such that a gap is formed at the seat; and (iv) a flow restriction disposed downstream of the gap, wherein when the valve is actuated, fluid is allowed to flow from the supply port through the first opening and the gap and through die flow′ restriction prior to flowing through the second opening to the operating port, such that the flow restriction generates an increased pressure level at the gap.

When a first control valve and a second control valve are in non-neutral positions, respectively, a fifth fluid passage and a second fluid passage are closed, thereby generating a first pressure within a fifth portion of the fifth fluid passage and a second pressure within a second portion of the second fluid passage, so that the first pressure is applied to a first valve through a fourth fluid passage to move the first valve to close the third fluid passage and a second pressure is applied to the confluence valve through a first fluid passage to move the confluence valve to a confluence position. When the confluence valve is in the confluence position, the confluence valve directs working fluid from a first working fluid supply to the second control valve.

A hydraulic system for a working machine includes a hydraulic pump to output a hydraulic fluid, an operation device operable to supply a pilot fluid in accordance with an amount by which the operation device is operated, a hydraulic actuator to be operated by the hydraulic fluid, a pilot fluid passage connected to the operation device, a first control valve connected to the pilot fluid passage and to be operated by the pilot fluid to control a flow of the hydraulic fluid, a second control valve to be operated by the pilot fluid to control a flow of the hydraulic fluid, a proportional valve to change a pressure of the pilot fluid to operate the second control valve, a pressure detector provided in the pilot fluid passage to detect a pressure in the pilot fluid passage, and a controller to control the proportional valve based on the pressure.

A hydraulic machine. A boom actuator includes a large chamber and a small chamber. A recovery unit receives fluid discharged from the large chamber and then recovers energy. A recovery line connects the large chamber and the recovery unit. An accumulator is connected to a first point on the recovery line. A discharge valve is disposed on the recovery line between the first point and the recovery unit. A first sensor measures a pressure in the accumulator. A controller controls opening and closing of the discharge valve. The controller performs anti-bouncing control of: determining a target pressure in the accumulator corresponding to a load pressure applied to fluid in the large chamber by a load according to a predetermined correspondence; and controlling the opening and closing of the discharge valve such that the pressure in the accumulator measured by the first sensor reaches the target pressure.

A system and method for detecting the functional state of a piloted or direct-operated isolation valve in a hydraulic circuit is presented. In some examples the hydraulic circuit is a steering circuit and the isolation valve provides selective isolation between a hydraulic actuator and one or more metering valves. In some examples, the isolation valve assembly is movable between a first position, in which fluid flow between the metering valve and the actuator is enabled, and a second position, in which fluid flow between the metering valve and the actuator is blocked. When the isolation valve assembly is moved to one of the first and second positions, an inlet port and a pressure sensing port of the isolation valve assembly are placed in fluid communication with each other. When the isolation valve assembly is moved to the other of the first or second position, a second inlet port and the pressure sensing port are placed in fluid communication.