Yanmar 4LHA-DTP, Operation Manual

Page: 365 / 670

Chapter 3 Fuel Injection Equipment
5. Injection Pump Construction and Operation
Injection Timing Control
Roller holder
Roller holder pin
High
pressure
side
Timer piston
Timer spring
i 4LHA Series
The piston is positioned in the center of the
timer in the lower part of the injection pump.
On the low pressure side of the timer piston
there is a timer spring with a predetermined set
force; the pump chamber fuel oil pressure acts
on the opposite side (high pressure side). The
timer piston position changes in accordance
with the balance of these two forces, to rotate
the roller holder via the roller holder pin. When
the timer piston compresses the timer spring,
the injection timing is advanced (the roller
holder rotates in the reverse rotation direction),
and due to timer piston movement in the oppo-
site direction the injection timing is retarded.
Injection timing is controlled by the above.
:
ig. 6 Cutaway view of injection timing control
Feed Pump
Regulating
From fuel filter
v a
| v e
Rotor
To pump
" chamber
Key
Blade
Drive shaft
Fig. 7 Feed pump operation
The feed pump comprises a rotor, blades and
liner.
Drive shaft rotation is transmitted through a
key to rotate the rotor.
The inside circumference of the liner is eccen-
tric to the centre of rotor rotation. Four blades
are installed in the rotor. Centrifugal force
forces the blades outwards during rotation to
contact the inside surface of the liner and form
four fuel oil chambers. The volume of these four
chambers increases through rotor rotation to
suck fuel oil from the fuel tank. Conversely,
when the volume of these four chambers de-
creases fuel oil is pressurized.
3-1-a