PRINCIPLES GASOLINE/DIESEL FURL SYSTEMS - OD1620 - LESSON 2/TASK 2
has a separate cam for each pump plunger. Also, the metering of the fuel is
accomplished by a single axially located rotary valve in the wobble plate
unit, whereas the rotary movement of the individual plungers controls the
amount of fuel in the multiple unit injection pump.
(2) Wobble Plate Pump Principles. A plate is mounted on a shaft and
set at an angle to it so that as the shaft rotates, the plate moves
laterally in relation to any given point on either side of it.
The pump
derives its name from the fact that the plate appears to wobble back and
forth as it rotates.
The end of the push rod is placed in a guide plate
that lays against the wobble plate. The push rod is held in a bore in the
pump body so that it can move only in a direction parallel to the wobble
plate shaft. The rotation of the wobble plate then causes the guide plate
to wobble, thus moving the push rod back and forth.
The push rod is
connected to the pump plunger so that movement to the left actuates the pump
on its delivery stroke and a spring returns it on the suction stroke.
(3) The Wobble Plate Injection Pump.
As in the multiple unit
injection pump, the wobble plate injection pump contains an individual
plunger-type pump for each cylinder. The pump plungers are spaced equally
about the wobble plate. As the wobble plate rotates, it will actuate all of
the individual injection pumps. At any given time during rotation, half of
the plungers will be moving on their delivery stroke while the other half
will be on their return stroke.
(a) The rotary metering valve is driven by the same shaft that
drives the wobble plate. The rotary valve consists of a lapped cylindrical
shaft that is fitted closely in a barrel to prevent fuel from escaping at
its ends. Fuel is admitted to the barrel at the center of the valve, which
contains a spoonlike reduction in diameter. This reduction in diameter acts
as a fuel reservoir.
(b) The reduced portion of the valve is in the shape of a band
broken by a triangular land that is the same diameter as the ends of the
valve.
The reservoir created by the reduced portion of the valve is
connected to each pump cavity by individual ports so that the pump cavities
may be supplied with fuel. This reservoir receives a
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