TM 5-3805-281-24-1
Theory of Operation
as the control signal to the valve function increases.
The arm regenerative (SC) (B), speed sense (SD) (C),
When the control signal becomes equals to or greater
propel speed change (SI) (D) and power boost (SG)
than the magnetic force, the spool is pushed to the
(E) solenoid valve are proportional solenoid valve (R)
right closing the passage stopping the pressure
type. The solenoid valve coil is energized by a
increase. The reduced pilot oil control signal to the
electrical signal from the engine and pump controller
valve function is trapped. The spool is moving
(EPC). The electrical signal is a DC voltage that is
constantly to maintain the control signal in response to
turned on and off to form a pulse width modulated
the electrical signal to the solenoid coil.
signal. The solenoid coil (I) reacts to the average
voltage to create a magnetic force to shift the spool (F)
For circuit operation of arm regenerative solenoid
left against a spring. The reduced pilot oil (P) control
valve, see Arm Regenerative Valve Operation in this
signal sent to the valve function (L) depends on how
group.
long the electrical signal in on verses on how long it is
off. The reduced pilot oil control signal is in proportion
For circuit operation of speed sensing solenoid valve,
to the electrical signal to the solenoid coil.
see Engine Speed Sensing Control Circuit Operation in
this group.
When de-energized (G), the spool is pushed to the
right by a spring. The valve function port is connected
For circuit operation of propel speed change solenoid
to the hydraulic oil tank (J) port.
valve, see Propel Speed Change Circuit Operation in
this group.
When energized (N), the magnetic force shifts the
spool left against the spring. Pilot oil (O) flows past the
For circuit operation of power boost solenoid valve,
spool flange and out the valve function port as a
see Power Boost Control Circuit Operation in this
reduced pilot oil (P) control signal. Because the flange
group.
on the right is larger than the flange on the left, the
spool is pushed to the right against the magnetic force
9025
05
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CED,TX08227,3114
1901MAY982/2
6-29
