centrifugal governor

a mechanism for maintaining automatically a specified rate of rotation of a shaft on a regulated object (such as an engine or turbine) by means of a sensor in the form of rotating weights; the centrifugal force on the weights is used to move an element that regulates the object. The first centrifugal governor designed for this purpose was installed on Watt’s steam engine in 1784. Modern versions have one, two, or more rotating weights. When the rate of rotation of the shaft changes, the centrifugal force on the weights is altered, thereby causing a movement of the governor sleeve and the associated regulating element. When the specified rate of rotation has been reestablished, the sleeve is restored to its initial position by means of springs.

A centrifugal governor may operate directly or indirectly, depending on its purpose. In a direct-action governor, a movement of the sleeve results in a movement of the element that regulates the object. If the force needed for this movement is substantial, an indirect-action governor is used. In this case, the centrifugal force on the weights is used to move a slide valve, which acts as the control element of an amplifying device—a hydraulic servomotor having a piston that is linked by a rod to the element that regulates the object. An indirect-action governor has a feedback lever, by means of which a movement of the piston restores the original position of the slide valve or the tension on the spring.

Modern centrifugal governors may also be used to change a specified angular velocity, to provide remote control of an object, and to limit loading. Direct-action centrifugal governors are used on diesel engines in tractors and motor vehicles; indirect-action governors are used on stationary and marine diesel engines and on steam and hydraulic turbines.