TM 5-3805-263-14&P-3
HYDRAULIC SYSTEM
AND STEERING
The low pressure setting of the pump is approximately
load on the component, the pressure of the oil in this
2150 psi (151.1 kg/cm2). The pump operates with this
circuit gets an increase. When the pressure of the oil in
pressure at all of the control valves in the hydraulic
the circuit gets to 1500 psi (103.5kg/cm2), the pressure
system when the engine is running and the control
of the oil in line (12) moves shuttle valve (I I). When the
valves are in HOLD position. When a control valve is
shuttle valve is moved, the pressure of the oil from the
used, the pressure of the oil in the circuit to the
pump into the hydraulic circuit can go as high as
component is also in line (12) to shuttle valve (11).
approximately 3500 psi (246.1 kg/cm2).
When there is an increase in the
Servo Valve, Pressure Reduction Valve and Shuttle Valve
SERVO VALVE CROSS SECTION
(Pistons in pump at longest stroke)
1. Passage for oil from the case. 2. Valve spool. 3. Groove {(three) in valve spool. 4. Passage to case. 5. Piston
assembly. 6. Cartridge for servo valve. 7. Chamber. 8. Sleeve. 9. Passage for oil at pump output pressure. 10. Hole
and passage to the case. 11. Passage for oil from pressure reduction valve.
The actions of the servo valve and the pressure
into the pressure reduction valve, through passage (18),
reduction valve change the angle of swashplate (14).
and through the orifice in piston (17). The orifice makes
The change in the angle of the swashplate changes the
a reduction in the pressure of the oil that goes through
stroke of the pistons. When the stroke of the pistons
passage (II 1) in the cartridge for servo valve (6). The
change, the gpm (litre/min) output of oil from the pump
force of the oil through passage (11), and on the larger
changes.
surface of valve spool (2), is the same as the force
spring ( 13) has on the valve spool.
When the engine is not running, the swashplate is at the
maximum angle.
The swashplate can be at the
When there is an increase in the pressure of the output
maximum angle when the engine is running and two
oil from the pump, there is also an increase in the
components in the hydraulic system are being operated
pressure of the oil through passage (9) and passage (I I).
together. The pistons, in the barrel assembly of the
pump, have their longest stroke when the swashplate is
The increase of the pressure of the oil, through passage
at its maximum angle.
(11) and on valve spool (2), is now more than the force
of spring (13) and valve spool (2) moves. The oil in
Oil at the output pressure of the pump goes into cartridge
passage (9) is now stopped by the valve spool. The
(6), through passage (9), around valve spool (2) and
position of valve spool (2) can now let the oil in chamber
goes through passages in sleeve (8) and cartridge (6),
(7) go through passages in cartridge (6), sleeve (8), and
into chamber (7). The oil in chamber (7) keeps piston
through grooves (3), to the hole and passage (10) to the
assembly (5) at its extension and the swashplate (14) at
case.
its maximum
angle.
Oil, at the outlet pressure of the pump, also goes
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