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4.
Injection timing and effective starting
When the plunger closes suction port of the barrel, forced
delivery of fuel starts. But fuel
is
not injected from the noz-
2le.at ence because of contraction of,fuel,'etc.
.
Injection timing of this engine is fixed constant
(23O
before
TDC)
irrespective of engine rpm. On the other hand, in start-
ing,
a
proper delay from the timing for
high
speed running
and increased fuel injection is indispensable for effective
starting.
For
this purpose
a
notch is
made
at the plunger
head, whch reserves to delay the injection timing by nearly
8"
to facilitate starting. (See Fig.
57.)
INSTALLED ONLY
TO
DY30
Fig.
57
5.
Function
of
the delivery valve
By the plunger stroke, fuel pressure is raised. And when it becomes higher than the pressure remained in the
high
pressure
pipe, the delivery valve spring is pushed down and the valve opens.
As
the result, the fuel
in
the
high
pressure pipe is delivered
forcibly.When the plunger lead meets suction port of the plunger barrel, deliveryof fuel ends, and the delivery valve
is
closed
by the
spring
tension of the valve. At this time, delivery valve prevents reverse
flow
of the fuel.
Also
suction back motion
around the upper part of the plunger sucks back the fuel
in
the equal amount of the stroke [A] and decreases remaining
pressure in the
high
pressure pipe. The nozzle jets the fuel clearly off and prevents after dripping. (See Fig.
58.)
!I!
/
DELIVERY VALVE SPRING
DELIVERY VALVE
ION BACK
STROKE
Fig.
58
6.
Function
of
the damping valve
The damping valve is assembled in the end
of
injection
pump and it reaches the
seat
before arrival of delivery valve
at the seat. The
small
orifice
in
the valve
is
the passage
of
fuel to the chamber
in
the delivery valve holder. Accordhg-
ly, descending velocity of the delivery valve
is
decreased,
which prevents the negative pressure being produced sud-
denly.
As
a result, proper injection is conducted and the
DEL,VERY
VALVE
DAMPING VALVE
engine noise is decreased. (See Fig.
59.)
-
31
-
Fig.
59