General Description Of Auxiliary Gadgets And Parts; Fuel Injection Pump Mechanism - Robin America DY30 Service Manual

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 t o 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 u p 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."
D A M P I N G V A L V E
D E L I V E R Y V A L V E
V E R T I C A L HOLE
PLUNGER BARREL
I N T A K E
PORT
(EXHAUST PORT)
PLUNGER
L E A D
EFFECTIVE STROKE
Fig. 54
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29
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