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 TM 9-8000
(2) As the cam lobe comes around again, It
the pump chamber reaches the desired maximum. This
forces the plunger upward. This forces the fuel out of
effectively regulates pump pressure.
the chamber through the outlet valve and the Injection
pump.
5-23. Gear-Type Supply Pump. The basic overall
operation of the gear-type supply pump Is the same as
(3) The cam follower drives the plunger
the gear-type oil pump (para 20-4).
through a spring. The spring Is calibrated so that it will
flex rather than drive the plunger when the pressure In
Section V. GOVERNORS
counterbalanced by springs. When the speed of the
5-24. General. All diesel engines require governors
engine increases, the weights fly outward, pulling with
to prevent overspeeding of the engines under light
them suitable linkage to change the setting of the pump
loads. Automotive diesel engines also demand control
control rod. The governor linkage is connected to the
of idling speed.
Any of the governors provide a
injection pump in such a manner that the spring moves
variable-speed control that, In addition to controlling
the control mechanism toward the full-fuel position. The
minimum and maximum speeds, will maintain any
outward movement of the governor fly-weights, through
intermediate speed desired by the operator.
Engine
the sliding governor sleeve, will move the pump control
speed in a diesel Is controlled by the amount of fuel
rod toward the no-fuel position against the force of the
injected. The Injection, therefore, is designed to supply
governor spring.
the maximum amount of fuel that will enable it to operate
at full load while reaching a predetermined maximum
b. With this type of governor, the operator controls
speed (rpm).
If, however, the maximum fuel charge
the tension of the governor spring to control the quantity
were supplied to the cylinders while the engine was
of fuel rather than operating the fuel control rod directly.
operating under a partial or unloaded condition, the result
The fuel delivery control system of the injection pump is
would be overspeeding and certain failure. Thus, it can
connected to the governor yoke in such a manner that
be seen that the governor must control the amount of
any movement of the yoke will affect directly the quantity
fuel injected in order to control the engine speed.
of the fuel injected. The spring tension is controlled by
the operating lever, the movement of which is
5-25. Actuation. Governors may be actuated through
determined by the position of the foot throttle. The travel
the movement of centrifugal flyweights or by the air-
of the operating lever is limited by the idle and maximum-
pressure differential produced by a governor valve and
speed screws. When the weights are fully collapsed
venturi assembly.
(engine stopped), the spring moves the sliding sleeve
and yoke so that the fuel injection pump is in the full-fuel
The centrifugal flyweight type may incorporate a
position.
When the weights are fully extended, the
mechanical linkage system to control the injection pump,
sliding sleeve and the yoke move to the rear and
or it may include a hydraulic system to transmit the
decrease the amount of fuel delivered.
action of the weights to the pump. On engines where
the rate of acceleration must be high, the governor-
c. If the load on the engine is decreased, the
controlling weights must be small to obtain the required
engine tends to accelerate. However, when the engine
rapid response from the governor. The problem is that
does accelerate, the increased centrifugal force causes
the smaller flyweights will not exert enough force to
the governor flyweights to move outward, resulting in the
control the injection pump properly. When this is the
movement of the fuel control rod through the governor
case, the flyweights will be used to control a hydraulic
sleeve toward the no-fuel position. This will cause an
relay valve, which, in turn, will control the Injection pump
equilibrium to develop between the flyweights and the
through a servo piston.
governor spring. The movement of the operating lever
varies the spring tension. This will cause a change in
5-26. Mechanical
(Centrifugal)
Governors
the point of equilibrium between the
a. The operation of the mechanical governor is
based on the centrifugal force of rotating weights
5-30
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