Anti-reverse valve

An anti-reverse valve configured to prevent a reverse action of an actuator immediately after stoppage, comprising:

• a valve housing having a first supply and discharge passage connected to one of a pair of main passages through which a working fluid is supplied to and discharged from the actuator, a second supply and discharge passage connected to the other main passage, and a drain passage connected to a tank;
• a spool slidably accommodated in the valve housing, the spool being movable to a first communication position at which the first supply and discharge passage and the drain passage communicate with each other, a second communication position at which the second supply and discharge passage and the drain passage communicate with each other, and a neutral position at which communication between the first supply and discharge passage and the drain passage is blocked and communication between the second supply and discharge passage and the drain passage is blocked;
• a first pressure chamber to which the working fluid that biases the spool toward the second communication position is led;
• a second pressure chamber to which the working fluid that biases the spool toward the first communication position is led;
• and
• a biasing member configured to hold the spool at the neutral position, wherein
• a first communication passage that allows the first supply and discharge passage to communicate with the first pressure chamber irrespective of the position of the spool, and a second communication passage that allows the second supply and discharge passage to communicate with the second pressure chamber irrespective of the position of the spool are provided inside the spool,
• a first restrictor configured to apply resistance to the passing working fluid is provided in the first communication passage,
• a second restrictor configured to apply resistance to the passing working fluid is provided in the second communication passage, and
• a first annular groove that allows the first supply and discharge passage to communicate with the drain passage when the spool is placed at the first communication position, and a second annular groove that allows the second supply and discharge passage to communicate with the drain passage when the spool is placed at the second communication position are provided in an outer periphery of the spool.