6-2
FUEL
INJECTION
PUMP
0
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 satisfy the following functions.
6
-
2
-
1
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 varied by the governor to suit to varying load.
This engine has no automatic advancing device, but in starting (max. delivery), the
injection timing is to be delayed.
6-2-
2
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.
62.)
(1
)
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.”
(2)
FORCED
SUPPLY
OF
FUEL
I
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
pressurized 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, andq then
it
injects the fuel into combustion chamber.
This
is
on the stage of “pressurized supply.”
DAMPING
DELIVERY
VERTICAL
HOLE
PLUNGER
PLUNGER
SUCTION PORT
(DELIVELY
PORT)
LEAD
VALVE
VALVE
BARREL
EFFECTIVE STROKE
FIG.
62
-
40
-
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