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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
t h e . 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 i t 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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