TABLE OF CONTENTS In Chapter 21 we learned that flywheels are used to regulate speed over short intervals of time such as a single revolution or the duration of an engine cycle. Governors, too, are devices used to regulate speed. In contrast to the flywheel, however, governors are used to regulate speed over a much longer interval of time; in fact, they are intended to maintain a balance between the energy supplied to a moving system and the external load or resistance applied to that system.
When the speed of a machine must, during its lifetime, always be kept at the same level, or approximately so, then a shaft-mounted mechanical device may be an appropriate speed regulator. Such governors may be classified as
Centrifugal governors
Inertia governors
As the name indicates, centrifugal force plays the important role in centrifugal governors. In inertia governors it is more the angular acceleration, or change in speed, that dominates the regulating action.
The availability today of a wide variety of low-priced solid-state electronic devices and transducers makes it possible to regulate mechanical systems to a finer degree and at less cost than with the older all-mechanical governors. The electronic governor also has the advantage that the speed to be regulated can be changed quite easily and at will.
Figure 22.1 shows a simple spring-controlled centrifugal shaft governor. Masses attached to the bell-crank levers are driven outward by centrifugal force against springs. The motion of the shaft-mounted sleeve is dependent on the...
