1. Field of Invention
The present invention relates to the speed governors and distributing valves for hydraulic turbines and pump turbines, and particularly to three-way distributing valves for the speed governor of hydraulic turbines or the like.
2. Related Art
Three-way distributing valves are used in a speed governor for controlling a hydraulic servomotor driving the guide vanes for adjusting the volume of water that enters a hydraulic turbine or a pump turbine. An example of the three-way distributing valve for the speed governor of hydraulic turbines or pump turbines is disclosed in Patent Document 1, in which a hydraulic amplifier (three-way distributing valve) is disposed such that the plunger (main valve) can be moved vertically. The plunger is driven by a control piston that is vertically moved by pressure oil supplied via a pilot valve. Because the plunger is adapted to be moved up and down by the control piston, the control piston is directly connected to the main valve in an integral structure.
Patent Document 1: JP Patent Publication (Kokai) No. 2000-18145 A