TM 5-3805-280-24-1
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 equal 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 is activated by an electrical
increase. The reduced pilot oil control signal to the
signal from the engine and pump controller (EPC). The
valve function is trapped. The spool is moving
electrical signal is a DC voltage that is turned on and
constantly to maintain the control signal in response to
off to form a pulse width modulated signal. The
the electrical signal to the solenoid.
solenoid (I) reacts to the "average" voltage to create a
magnetic force to shift the spool (F) left against a
For circuit operation of arm regenerative solenoid
spring. The reduced pilot oil control signal sent to the
valve, see Arm Regenerative Valve Operation in this
valve function (L) depends on how long the electrical
group.
signal is on verses on how long it is off. The reduced
pilot oil control signal is in proportion to the electrical
For circuit operation of speed sense solenoid valve,
signal to the solenoid.
see Engine Speed Sense 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
29
TX,9025,GG2095 1920MAY982/2
6-28
