Valve device

A valve device that changes a direction of flow of a hydraulic fluid supplied to and discharged from a cylinder mechanism to actuate the cylinder mechanism, the valve device comprising:

• a control valve comprising a main spool axially movable between different positions, the control valve being connected to the cylinder mechanism via a first supply/discharge path and a second supply/discharge path through which the hydraulic fluid is supplied to and discharged from the cylinder mechanism, the control valve being configured to, when the main spool has moved to a first position, allow the hydraulic fluid to be supplied to the cylinder mechanism through the first supply/discharge path and discharged into a tank through the second supply/discharge path, the control valve being further configured to, when the main spool has moved to a second position, allow the hydraulic fluid to be supplied to the cylinder mechanism through the second supply/discharge path and discharged into the tank through the first supply/discharge path, the control valve being further configured to, when the main spool has returned to a neutral position, block flow of the hydraulic fluid to the cylinder mechanism through the first and second supply/discharge paths;
• a lock valve comprising a plunger disposed in the first supply/discharge path to open and close the first supply/discharge path, a biasing member biasing the plunger in a closing direction in which the plunger moves to close the first supply/discharge path, and a pressure chamber into which a pressure is introduced and which applies the introduced pressure to the plunger in the closing direction, wherein a hydraulic pressure of the hydraulic fluid flowing in a cylinder mechanism-side portion of the first supply/discharge path and a hydraulic pressure of the hydraulic fluid flowing in a control valve-side portion of the first supply/discharge path are applied to the plunger to act against a biasing force of the biasing member and the pressure applied by the pressure chamber, the cylinder mechanism-side portion being a portion closer to the cylinder mechanism than the plunger, the control valve-side portion being a portion closer to the control valve than the plunger;
• and
• a selector valve comprising a selector spool operable in conjunction with the main spool to axially move between different positions, the selector valve being configured to, when the main spool moves to the first position or the neutral position, move the selector spool to a holding position to bring the pressure chamber into communication with the cylinder mechanism-side portion of the first supply/discharge path to introduce a pressure of the cylinder mechanism-side portion into the pressure chamber, the selector valve being further configured to, when the main spool moves to the second position, move the selector spool to an open position to bring the pressure chamber into communication with the tank to introduce a tank pressure into the pressure chamber, the selector spool being located adjacent to the main spool and having an axis crossing an axis of the main spool.