TM 5-3805-281-24-1
Theory of Operation
against the supply oil pressure opening a path for oil to
Summation is the flow rate of a pump controlled by
flow from the large end of servo piston to return. Also
monitoring both pump pressures. The pump supply oil
engine output is not exceeded even if one pump is
pressure (load) for each pump is sensed at the load
loaded relatively high while the other pump stays
piston (11) through the pump pressure inlets (12) at its
relatively low.
regulator and at the regulator of other pump. The rear
pump supply oil pressure is sensed on the end of load
Speed Sensing operates when the actual engine
piston in each pump regulator. The front pump supply
speed, as measured by engine speed sensor, is pulled
oil pressure is sensed on the shoulder of load piston in
down to the target engine speed, as set by engine rpm
each pump regulator. The area on the end of load
dial. The speed sensing solenoid valve coil is
piston and the shoulder are equal. Therefore, the force
energized by an electrical signal from the engine and
applied through the load spool (10) to the inner and
pump controller. A reduced pilot oil control signal is
outer springs is an average of the pump supply oil
sent to the end of load piston at the speed sense
pressures. The springs are adjusted against the
signal port (13) in the front and rear pump regulators.
average pressure so the flow rate of the pumps are
The reduced pilot oil control signal along with the
approximately equal and each pump uses
pump supply oil control signals shifts the load spools
approximately half the engine output.
against the springs opening a path for pilot oil to flow
to the servo piston large end. The pilot oil pressure
If the load on either pump increases, the average
applied to the servo piston large end pushes the piston
pressure on the load pistons pushes the load spools
up against the pressure applied to the small end
against the springs opening a path for pilot oil to the
decreasing pump angle. The flow rate of both pumps
large end of servo pistons. The flow rate of both
decrease so the load on the engine decreases and the
pumps decrease so the load on the pumps do not
actual engine speed can increase.
exceed the engine output. If the load on the pumps
decrease, the springs push the load pistons to the right
9025
05
24
CED,TX08227,3113
1930APR982/2
6-24
