Yanmar 4LHA-HTP Operation Manual page 398

Chapter 3 Fuel Injection Equipment
7. Timer Construction and Operation
Timer spring Servo valve
Low pressure chamber
Fig. 49 Servo valve timer operation: when
pump chamber pressure has decreased
Timer spring Servo valve
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High pressure chamber
Low pressure chamber
Fig. 50 Servo valve timer operation: maximum
advance position
Bushing
High pressure chamber
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When pump chamber pressure has
decreased
From the stable condition,
pressure has decreased and the servo valve is
moved to the right (Fig. 49) by the timer spring
force. The timer's high pressure chamber and
the timer's low pressure chamber are con-
nected through the passage in the servo valve.
Therefore the timer high pressure chamber's
high pressure escapes to the timer's low pres-
sure chamber and the timer piston moves in
the retard direction (to the right in Fig. 49), and,
as in the above, a stable condition results.
Maximum advance position
As the pump chamber pressure has completely
overcome the timer spring force, the timer pis-
ton moves until its end face contacts the timer
cover's low pressure chamber side. That is, if
pump chamber pressure further increases, the
timer piston cannot move further in the ad-
vance direction. This position is the maximum
advance position.
According to the above, if the timer piston is
moved through the driving reaction force, op-
erations identical to the above (when pump
chamber pressure has increased or decreased)
will be repeated until the stable condition is
attained.
3-1-41
4LHA Serie.
pump chamber