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7.
GENERAL DESCRIPTION
of
AUXILIARY
GADGETS
and
PARTS
7-1
FUEL
INJECTION
PUMP
MECHANISM
It
is
not too much to say that the fuel injection pump is the heart of the diesel engine, and it must be precise enough to sat-
isfy the following functions.
Function
Injecting fuel, starting with
high
pressure and ending with low pressure.
Injecting the predetermined amount of fuel accurately at each stroke.
Injecting fuel at specified time within a specified time interval.
Quantity being injected is closely vaned by the governor to suit to varying load.
This
engine has no automatic advancing device, but in starting (max. delivery), the injection timeing
is
to be delayed.
Theory
of
the
injection pump mechanism
The
plunger of the injection pump
is
pushed up by the cam of the camshaft, and it is pushed down
by
the plunger spring. By
this up
and down motion in a stroke, suction and forced supply of fuel are conducted. (See Fig.
54.)
Suction of fuel
Through the filter in the fuel tank, fuel
is
supplied and is
in
full around the intake port of the plunger barrel. When
the top of the cam lobe passed the tappet and cam function ended, plunger spring pushes down the plunger.
When the plunger is pushed down passing the fuel intake, fuel
is
sucked into the barrel, and suction is continued until
arrival
of
the plunger at the bottom of its stroke.
This
is on the stage of "suction."
Forced supply of fuel.
The camshaft rotates and pushes up the plunger. Forced supply of the fuel is started only when the upper part
of
the
plunger closed the fuel intake in the course of being pushed up by the cam rotation. The fuel in the barrel is pressur-
ized by a,very strong force
(100
kg/cm2 and up), and as a result, the force of the fuel pushes up the delivery valve and
the damping valve, and then it injects the fuel into combustion chamber.
This
is on the stage of "pressurized supply."
DAMPING VALVE
DELIVERY VALVE
VERTICAL
HOLE
PLUNGER BARREL
INTAKE
PORT
(EXHAUST PORT)
PLUNGER
LEAD
EFFECTIVE STROKE
Fig.
54
-
29
-