S Y S T E M S O P E R A T I O N
S T E E R I N G S Y S T E M
A M P L I F I E D S T E E R I N G S Y S T E M
STEERING CONTROL VALVE
STEERING CONTROL VALVE IN NEUTRAL
1. Metering orifices.
9. Inlet (from right
15. Inlet (from steering
10. Inlet (from left
16. Sail resolver valve.
4. Outlet for left turn.
5. Outlet to tank.
1S. Flow control valve.
6. Outlet for right turn.
19. Pilot valve (relief
7. Metering orifices.
13. Return paaaage.
The flow of pilot oil to either end of valve spool
(12) is stopped when; (a) rotation of steering wheel is
stopped, or (b) the neutralizer valve stops the flow
after a complete turn has been made. With no pilot
oil flow against either end of the valve spool, spring
(8) will keep the spool in its NEUTRAL postion.
When the steering control valve is in its NEU-
TRAL position, the oil from the steering pump sec-
tion is stopped by the valve spool. The pressure in-
creases in inlet passage (15). This pressure increase
moves flow control valve (18). The flow control valve
moves until oil can flow through it to outlet (5).
In the NEUTRAL position, the valve spool also
blocks (stops) the oil in the lines to the cylinders. This
holds the machine in the turned position where the
steering wheel was stopped.
The pressure of the oil in blocked outlet (4) or
(6) is felt through ball resolver valve (16) and
against pilot valve (19). If an outside force tries to
turn the machine when the valve spool is in the
NEUTRAL position, the increase in pressure in
outlet (4) or (6) will open pilot valve (19). The pres-
sure in the lines will not go higher than the relief
valve setting [17 200 ± 340 kPa (2500 ± 50 psi)].
When the pilot flow to one end of the spool stops,
part of the oil on that end of the spool must be
removed before the valve spool can return to the
NEUTRAL position. To do this, part of the oil is
pushed, by the force of spring (8), to the opposite end
of the spool. The spool can then move to its neutral
As an example, a left turn is made and pilot oil
flows through inlet (10). The pressure of the oil from
inlet (10) causes spool (12) to move to the right.
When the pilot flow stem, part of the oil from the
left end of the spool must be removed so that the spool
can move to the NEUTRAL position. The force of
spring (8) causes the spool to move to the left. As the