Figure 4-72. Centrifugal Governor.
will exert more pressure on one side of the throttle valve
than on the other. Also, the throttle valve must be limited
(2) The damper piston prevents fluctuation of
from opening all of the way. This is because the throttle
the throttle valve that would occur due to pulsation of the
valve could not be pushed closed during full throttle
intake mixture caused by the time between, or the
applications if it were perpendicular to mixture flow. The
overlapping of, the intake strokes.
following two subparagraphs demonstrate the two
variations of this type of governor.
(3) During periods of light loads, the engine
can reach its maximum governed speed with a relatively
a. Velocity-Vacuum Governor - Type I. The first
small throttle opening. This could cause the intake
mixture to close the throttle valve too much, causing
type of centrifugal-vacuum governor (fig. 4-73) uses a
excessive speed reduction. To prevent this, a vacuum
spring that tends to pull the throttle toward the open
compensator piston uses manifold vacuum to increase
position. The spring is attached on one end to a vacuum
the governor spring tension.
piston through an adjusting screw. The other end of the
spring is attached to the throttle shaft through a lever.
(4) The maximum governed engine speed can
There is also a damper piston connected to this lever.
be adjusted by loosening or tightening the engine-speed
Operation is as follows:
adjusting screw, which changes the tension of the
(1) As engine speed increases to the governed
maximum, the speed of the mixture forces the throttle
valve toward the closed position against the force of the