A method is provided for compensating for the flow rate of a variable capacity-type hydraulic pump such that, when a manipulation lever is manipulated, a discontinuous section, which has no change in the discharge flow rate of the hydraulic pump, is eliminated.

A main flow path that introduces high-pressure air to an air cylinder, or discharges exhaust air therefrom, includes a sub flow path provided alongside the main flow path; an exhaust flow rate adjustment unit that suppresses the operation speed of the air cylinder by adjusting the flow rate of the exhaust air flowing through the sub flow path; and a switching valve that is connected between the air cylinder, the main flow path and the sub flow path, and that connects the main flow path and the sub flow path to the air cylinder in a switching manner. The switching valve is constituted by a spool valve.

A gas cylinder includes supply passages for supplying, to an accommodation chamber, a part of gas supplied to a second port. When the pressure in a first pressure chamber is equal to or lower than a prescribed pressure, a valve element closes a discharge flow passage by the biasing force of a spring member and the pressure in the accommodation chamber. When the pressure in the first pressure chamber exceeds the prescribed pressure, the valve element is moved by the pressure in the first pressure chamber, against the biasing force and the pressure in the accommodation chamber, to thereby open the discharge flow passage.

A flow controller that changes the flow rate of air exhausted from an air cylinder in mid-stroke includes a first switching valve displaced from a first position to a second position under the effect of pilot air, and causing one port of the air cylinder to communicate with a first channel at the first position, exhausting air exhausted from the one port of the air cylinder while reducing the flow rate of the air using a first regulating valve at the second position. Since the pilot air is taken into the first switching valve from a second channel in a system different from the system of the first channel, a second regulating valve can be adjusted without being affected by the degree of opening of the first regulating valve.

A hydraulic system in a work machine includes a travel operation device provided in a pilot oil path between a hydraulic pump a travel pump and including an operation member and configured to generate a pilot pressure supplied via the pilot oil path and an additional pilot pressure in accordance with an operation amount of the operation member. The travel pump is to control a flow direction of hydraulic oil supplied to a travel motor based on the pilot pressure and the additional pilot pressure. A pressure selection valve is provided in a first coupling oil path to select a selected pressure from the pilot pressure and the additional pilot pressure to apply the selected pressure to the pilot hydraulic oil in the second coupling oil path. A pressure adjustment valve is provided in a second coupling oil path to control the selected pressure to be an adjusted pilot pressure.

There is provided a work machine that can limit operation of a work device by MC, and improves the responsiveness of a hydraulic actuator to operation of an operation device by an operator, and ensures operability equivalent to that of a work machine that does not have MC functions, and allows the hydraulic actuator for which the operation device is not being operated to automatically operate in either direction of the operation directions thereof. For this purpose, a drive system includes a selector valve 203a disposed between a secondary port 134a of an operation device 45a and a flow control valve 15a and between a proportional solenoid valve 54a and the flow control valve 15a and a selector valve 203b disposed between a secondary port 134b of the operation device 45a and the flow control valve 15a and between a proportional solenoid valve 54b and the flow control valve 15a. A controller 40 switches the selector valves 203a and 203b to either one of a first position and a second position on the basis of signals from pressure sensors 70a and 70b and pressure sensors 200a and 200b and target operation set in advance regarding the selector valves 203a and 203b.

A hydraulic excavator 1 includes an engine 16, a main hydraulic pump 17 driven by the engine 16, a plurality of hydraulic actuators driven with pressure oil discharged from the main hydraulic pump 17, a plurality of flow rate control valves adapted to control the flow rate of pressure oil to be supplied from the main hydraulic pump 17 to the respective hydraulic actuators, a pilot hydraulic pump 18 adapted to supply pressure oil for driving the flow rate control valves, and a controller 15 configured to control the discharge flow rate of the pilot hydraulic pump 18. The controller 15 controls the discharge flow rate of the pilot hydraulic pump 18 such that it becomes equal to the sum of requested pilot flow rates determined in accordance with control commands for the respective flow rate control valves and a preset standby flow rate.

A system for controlling hydraulic fluid flow within a work vehicle includes a pilot conduit fluidly configured to receive a pilot flow of the hydraulic fluid from a fluid supply conduit such that an operation of a compensator valve is controlled based on a pressure of the pilot flow. Furthermore, the system includes a pilot conduit valve configured to adjust the pressure of the pilot flow within the pilot conduit. A computing system is configured to determine the pressure of the hydraulic fluid within the fluid supply conduit downstream of the flow control valve based on the data captured by a pressure sensor. Furthermore, the computing system is configured to control an operation of the pilot conduit valve to selectively adjust the pressure of the pilot flow within the pilot conduit based on the determined pressure.

A continuous variable transmission (CVT) hydraulic pressure control device includes: a pressure regulation valve regulating an operation pressure of oil supplied to a friction element of a forward-rearward device; and a switch valve to respectively switch oil discharge paths through which the oil supplied to the friction element is discharged, respectively by a pilot pressure from the pressure regulation valve and an elastic force of a return spring. In particular, the oil discharge paths switched by the switch valve have oil flow resistances different from each other.

A shovel includes a lower traveling body, and an upper swiveling body mounted on the lower traveling body. The upper swiveling body is rotatable. An attachment is attached to the upper swiveling body. A traveling actuator is configured to drive the lower traveling body. An attachment actuator is configured to move the attachment. A control device is provided in the upper swiveling body. The control device is configured to autonomously operate at least one of the traveling actuator and the attachment actuator depending on an inclination of a ground on which the lower traveling body is traveling.