Patent ID: 7069723

Claim:
An anti-reaction valve device comprising: a casing provided with a primary port and a secondary port and a valve passage through which the primary and secondary ports fluidically communicate with each other; a plunger slidably provided in the casing; a sheet member slidably provided in the casing, the sheet member being movable to contact with the plunger to close the valve passage and being movable away from the plunger to open the valve passage; a spring drive means configured to drive the plunger and the sheet member by exerting a spring force to the plunger and the sheet member in such a manner that, the plunger and the sheet member move away from each other when a primary pressure of a hydraulic fluid on the primary port side is higher than a secondary pressure of a hydraulic fluid on the secondary port side, and a first difference pressure obtained by subtracting the secondary pressure from the primary pressure decreases from not lower than a first predetermined set difference pressure to not higher than a first open start difference pressure which is higher than the first set difference pressure at a speed not lower than a first predetermined reduction speed, and when the secondary pressure is higher than the primary pressure, and a second difference pressure obtained by subtracting the primary pressure from the secondary pressure decreases from not lower than a second predetermined set difference pressure which is lower than the first set difference pressure to not higher than a second open start difference pressure which is higher than the second set difference pressure at a speed not lower than a second predetermined reduction speed; and a one-way valve means provided between the secondary port and an open and close control chamber, and configured to inhibit a flow of the hydraulic fluid from the secondary port to the open and close control chamber.