Patent ID: 7225719

Claim:
A speed governor for controlling a hydraulic servomotor that drives guide vanes of a turbine, comprising: a distributing valve for feeding a control pressure oil to said hydraulic servomotor; a pilot valve for feeding the control pressure oil to said distributing valve; and an electromechanical transducer for driving said pilot valve in accordance with an electric signal sent from a control unit, wherein said distributing valve comprises: a plunger including a pressure oil switching valve; a valve seat disposed on an outer circumference of said plunger and including a pressure oil switching port; a body disposed on the outer circumference of said valve seat; and a plunger movement control unit for moving said plunger responsive to feeding of the control pressure oil from said pilot valve, wherein said distributing valve is disposed such that direction of movement of said plunger is horizontal, said distributing valve further comprising an air vent valve disposed at the highest position in a space formed in said body in which the pressure oil is contained.