Kubota EA330-E4 Series Workshop Manual page 52

EA330-E4, WSM
2) Delivery Valve
The delivery valve consists of the relief valve (1) and
delivery valve seat (2).
(1) Relief Valve
Delivery Valve Operation
Non-return Function
Time delay from the beginning of pressure-feeding of
the pump element to the beginning of nozzle
feed-injection becomes large when the delivery chamber
of the pump and the injection nozzle are in alignment and
the cut-off of fuel is also delayed. Then, simultaneously
with the completion of the pressure-feeding of fuel, the
delivery valve descends as a result of the action of the
delivery valve spring thereby forming a cut-off between
the delivery chamber and the injection pipe preventing
any reverse flow of fuel.
Reverse Suction Function (Dripping Prevention)
1. When the pressure-feeding of fuel ends, the delivery
valve lowers and relief valve (1) section comes into
contact with the valve seat.
2. Furthermore, the valve descends until seat surface
(2) is in contact with delivery valve seat (3) but as the
amount of fuel during interval "A" is sucked back
from inside the injection pipe, pressure within the
pipe is reduced giving improved cut-off of fuel
injection by the
subsequent dripping of the injectors.
(1) Relief Valve
(2) Seat Surface
(3) Delivery Valve Seat
Dumping Valve
At Fuel Injection
Since dumping valve is pushed up to press the
spring, fuel is pressure-fed to injection nozzle the same
as without dumping valve.
At Suck-Back
At suck-back by delivery valve after fuel injection,
fuel returns through dumping valve orifice. Generally
second injection is apt to occur by reflex pressure due to
reaction of sudden pressure drop when changing into
suck-back by delivery valve from high injection pressure.
As a result of preventing this second injection perfectly
by dumping valve and dissolving nozzle clogging,
durability of injection nozzle is improved.
(1) Dumping Valve
(2) Delivery Valve
(3) Orifice
1-M19
ENGINE
(2) Delivery Valve Seat
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nozzle, thereby preventing
(a) Non-return Function
(b) Reverse Section Function
(Dripping Prevention)
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(a) At Fuel Injection
(b) At Suck-Back
A: Suck-back Stroke
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KiSC issued 05, 2015 A