The DB2 fuel
injection pump uses a mechanical type governor (fig. 5-20). The governor function is that of
controlling the engine speed under various load settings. As with any mechanical governor,
it operates on the principle of spring pressure opposed by weight force, with the spring
attempting to force the linkage to an increased fuel position at all times. The
centrifugal force of the rotating flyweights attempts to pull the linkage to a decreased
the governor linkage varies the valve opening, thereby limiting and controlling the
quantity of fuel that can be directed to the fuel plungers. The position of the throttle
lever controlled by the operator's foot will vary the tension of the governor spring. This
force, acting on the linkage, rotates the metering valve to an increased or decreased fuel
position as required.
At any given
throttle position the centrifugal force of the rotating flyweights will exert force back
through the governor linkage which is equal to that of the spring, resulting in a state of
balance. Outward movement of the weights acting through the governor thrust sleeve can
turn the fuel-metering valve by means of the governor linkage arm and hook. The throttle
and governor spring position will turn the metering valve in the opposite direction.
is lubricated by fuel received from the fuel housing. Fuel pressure in the governor
housing is maintained by a spring-loaded ball-check return fitting (fig. 5-21)
in the governor cover of the pump.