TM 5-3805-280-24-1
Theory of Operation
9025
Control Valve Spool Actuated:
A pump control valve (Q) is located at the downstream
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When a single or combine functions are actuated the
end of the control valve neutral passage (H) in the left
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control valve spool shifts decreasing flow through the
and right control valves. The function of pump control
neutral passage and flow sense spool. As flow through
valve is to send a regulated pilot oil control signal to
the flow sense spool decreases, the spool is shifted to
the front and rear pump regulators to change pump
the left by the flow sense spring increasing the
flow in response to the actuation of control valve
pressure setting on the relief valve spring. The relief
spools.
valve spool shifts more closed decreasing pilot oil flow
to the hydraulic oil tank and increasing the control
Control Valve Spools in Neutral:
signal to the pump regulator which causes pump flow
When all control valve spools are in neutral the neutral
to increase. (See Hydraulic Pump Regulator Operation
passage through the control valve is not restricted and
in this group.)
full flow from the pump flows through the neutral
passage and flow sense spool (G) to the control valve
In addition, the control signal to pump regulators is
return passage (E). Full flow causes the flow sense
sensed by the pump control pressure sensors (L)
spool to move to the right against the flow sense
sending an electrical signal to the engine and pump
spring (F) decreasing the pressure setting of the relief
controller for the propel speed change function. (See
valve spring (D). The relief valve spool is pushed open
Propel Motor Speed Change Circuit Operation in this
to direct pilot oil to the hydraulic oil tank (I) decreasing
group.)
the control signal to the pump regulator (K).
TX,05,GG2178 1908JUN982/2
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