Abstract: A quick coupler circuit for attaching and detaching an attachment to a quick coupler includes a coupler cylinder, an actuator, a first hydraulic pump, a boosting valve, a coupler changeover valve, and a changeover switch. The boosting valve switches to a boosting position and the coupler changeover valve switches to a lock-side position when the changeover switch switches to a lock position. When the changeover switch switches to a hold position, the boosting valve switches to a non-boosting position and the coupler changeover valve switches to the lock-side position. When the changeover switch switches to an unlock position, the boosting valve switches to the boosting position and the coupler changeover valve switches to an unlock-side position.

Abstract: A quick coupler circuit for attaching and detaching an attachment to a quick coupler includes a coupler cylinder, an actuator, a first hydraulic pump, a boosting valve, a coupler changeover valve, and a changeover switch. The boosting valve switches to a boosting position and the coupler changeover valve switches to a lock-side position when the changeover switch switches to a lock position. When the changeover switch switches to a hold position, the boosting valve switches to a non-boosting position and the coupler changeover valve switches to the lock-side position. When the changeover switch switches to an unlock position, the boosting valve switches to the boosting position and the coupler changeover valve switches to an unlock-side position.

Abstract: An object of the present invention is to prevent an unnecessary large amount of hydraulic oil from being supplied to a cylinder when a working vehicle capable of performing both a loading operation and a digging operation is performing the digging operation. When one or a plurality of first digging operation conditions are satisfied and when a second operation condition that it is not detected that the loading operation is being performed is also satisfied, a control unit executes fluid amount reduction control of reducing the amount of hydraulic oil supplied from a first pump to a cylinder that actuates a work equipment.

Abstract: An object of the present invention is to prevent an unnecessary large amount of hydraulic oil from being supplied to a cylinder when a working vehicle capable of performing both a loading operation and a digging operation is performing the digging operation. When one or a plurality of first digging operation conditions are satisfied and when a second operation condition that it is not detected that the loading operation is being performed is also satisfied, a control unit executes fluid amount reduction control of reducing the amount of hydraulic oil supplied from a first pump to a cylinder that actuates a work equipment.

Abstract: A device which can easily adjust a relationship between a clutch pressure of an input clutch and a braking force (brake pressure) generated by a brake device to a desired relationship by a simple structure, in which a draining oil passage which is branched from an oil passage for supplying a pressure oil to the input clutch is provided, and the draining oil passage is communicated with a tank. The draining oil passage is provided with a pressure reducing valve which increases the pressure oil flowing through the draining oil passage depending on the valve position to decrease a clutch pressure of the input clutch. A brake operating member is mechanically coupled with a valve operating member of the pressure reducing valve, and the valve operating member of the pressure reducing valve is mechanically coupled with a valve operating member of the brake control valve by, for example, a spring.

Abstract: A device which can easily adjust a relationship between a clutch pressure of an input clutch and a braking force (brake pressure) generated by a brake device to a desired relationship by a simple structure, in which a draining oil passage which is branched from an oil passage for supplying a pressure oil to the input clutch is provided, and the draining oil passage is communicated with a tank. The draining oil passage is provided with a pressure reducing valve which increases the pressure oil flowing through the draining oil passage depending on the valve position to decrease a clutch pressure of the input clutch. A brake operating means is mechanically coupled with a valve operating member (spool) of the pressure reducing valve, and the valve operating member of the pressure reducing valve is mechanically coupled with a valve operating member (spool) of the brake control valve by, for example, a spring.

Abstract: In a hydraulic circuit system, when pressurized oil discharged from a single hydraulic pump is supplied to a plurality of actuators: the pressurized oil is supplied to heavily-loaded ones of the actuators at gradually reducing flow rates to reduce a shock, while supplied to lightly-loaded ones of the actuators at gradually increasing flow rates to increase working speeds of these lightly-loaded actuators. The hydraulic circuit system comprises a plurality of directional control valves (2) one of which is provided with pressure-compensated flow control valves (18) each of which is provided with a load lead-in passage having a restriction means (R). In addition, further comprised in the system are: relief valves (22, 22) for relieving the pressurized oil under the influence of load pressure of the actuators (3) operated by the directional control valves (2); a restriction orifice (24) provided in a drain side of each of the relief valves so as to produce pressure therein.

Abstract: This invention aims at providing a hydraulic circuit apparatus for supplying pressurized fluid into cylinders for a work implement arranged such that during normal operation of the work implement the flow rate of fluid discharged by a pump is controlled such that the difference between the discharge pressure of the pump and the load pressure is always kept constant, whilst during inching operation of the work implement the flow rate of fluid discharged by the pump is reduced.

Abstract: This invention provides a hydraulic circuit apparatus for operating a work-implement actuating cylinder arranged such that, during an earth compacting operation using a bucket, a work implement or boom is lowered by its own weight, and during other operations, a part of the fluid under pressure in a lifting chamber of the actuating cylinder is supplied together with pressurized fluid discharged by a pump into a lowering chamber to increase the retracting speed of a piston rod in the work-implement actuating cylinder. The apparatus comprises a spool slidably inserted in a valve bore formed in an operating valve body so that it may be moved between a first actuating position, where a second port connected to the lowering chamber is communicated with a second tank port and a first port connected to the lifting chamber is communicated with a first pump port; and a second actuating position, where the second port is communicated with a second pump port and the first port is communicated with a first tank port.

Abstract: This invention provides a hydraulic circuit apparatus arranged such that when each of operating valves is operated suddenly, the stability of each of actuators is improved, and when the operating valves are kept at their neutral positions, the flow rate of fluid discharged by a variable displacement pump is increased to improve the response of the hydraulic circuit, and when the actuators are supplied with pressurized fluid, pressure compensation is made by pressure compensating valves.

Abstract: A hydraulic circuit arranged to prevent the load pressure in one of the hydraulic actuators at the time of starting from becoming abnormally high thereby preventing fluid under pressure from being relieved by the safety valve when a plurality of hydraulic actuators are operated at the same time, wherein the function of one of the pressure compensating valves is temporarily enhanced by introducing the load pressure in the hydraulic actuator so as to supply a large quantity of fluid under pressure to the hydraulic actuator connected to the pressure compensating valve so that the operating speed of the hydraulic actuator can be increased.

Abstract: A pressure compensating type hydraulic valve wherein a pressure compensation can be made according to the movement of the movable portion of a hydraulic actuator, and the movable portion of the actuator can be stopped against load pressure when it is located at its neutral position. This pressure compensating type hydraulic valve is arranged such that a spool (24) is moved in a valve hole (16) so as to allow a first actuating port (21) and a second actuating port (22) connected with pressure receiving chambers (13.sub.1, 13.sub.2), respectively, defined on both sides of a movable portion (13.sub.