As the rotor revolves, its charging port registers
A positive displacement, vane-type fuel transfer
with one of six charging ports in the head. This rotor
pump is mounted at the end of the rotor shaft. Fuel
charging port connects perfectly to the pumping
pressure developed by the fuel transfer pump is
cylinder and axial passage of the rotor.
controlled by a pressure regulator valve in the pump
end plate. A passage at the top of the transfer pump aids
As the fuel enters the pumping cylinder, the
in removal of air introduced in the system. This passage
plungers are forced outward, a distance proportionate
connects with the pump housing through the fuel return
to the quantity of fuel to be injected. The quantity of
line to the supply tank.
fuel entering the pumping cylinder is controlled by the
fuel pressure at the charging ports, time available for
Fuel is drawn from the final filter into the pump
charging, and total plunger displacement available as
through the inlet strainer (fig. 4-40) by the vane-type
limited by the leaf spring.
fuel transfer pump. The fuel transfer pump capacity
greatly exceeds the fuel required for injection;
Fuel pressure at the charging ports is controlled by
therefore, a large percentage of the fuel from the pump
the metering valve and by the transfer pump pressure,
is bypassed through the pressure-regulating valve to the
which varies with engine speed. The time available for
inlet side of the pump. The quantity of fuel bypassed
charging is the length of time the charging port in the
increases as the pump speed increases. The bypass
hydraulic head remains in register with the charging
pressure also increases with speed.
port of the rotor. The length of time the charging port
remains in register depends entirely on engine speed.
Fuel not bypassed by the regulating valve passes
The maximum amount of fuel that can be injected is
through a hydraulic head passage to the metering valve.
limited by maximum outward travel of the plungers.
Fuel is metered by the metering valve in a quantity
This maximum plunger travel is limited by the roller
determined by engine demand.
shoes contacting the adjustable leaf spring stop. At the
time when the charging ports are in register, the rollers
are between the cam lobes (fig. 4-41); therefore, their
outward movement is unrestricted during the charging
cycle except as limited by the leaf spring.
3
The fuel is trapped in the cylinder for a very slight
4
interval of time after charging is complete. The
charging port of the rotor has passed out of register with
2
1
a charging port, and the head and the rotor discharge
5
port has not yet come into register with an outlet port of
the hydraulic head.
Further rotation of the rotor brings its discharge
6
port into register with an outlet passage in the hydraulic
ANNULUS
IN HEAD
METERING
ROTOR
VALVE
CAM RING
SHOE
ASf04040
7
FROM
TRANSFER
1.
Transfer pump blade
5. Regulating spring
PUMP
CHARGING
PLUNGERS
2.
Transfer pump liner
6. Regulating piston
RING
ROLLERS
ASf04041
3.
End plate adjusting plug
7. End plate plug
CHARGE
4.
Inlet strainer
Figure 4-41.--Rotor in charging position with the rollers
Figure 4-40.--Transfer pump (Model DC).
between the cam lobes (DC pump).
4-32
