Jeep J-10 Series 1982 Technical & Service Manual page 915

PRESSURE
RELIEF
VALVE FLOW
CONTROL
VALVE
CAP.
RESERVOIR
FILTER
ORIFICE
PRESSURE
PLATE
RETAINING
RING
DISCHARGE
CAVITY
SPRING
ROTOR
RETAINING
RING
END
PLATE
SEALS
PRESSURE UNION
AND FILTER
ASSEMBLY
AJ42080
Fig. 2L-2 Power Steering Pump
any turning effort applied at the steering wheel. As
front wheel resistance to turning effort increases, the
torsion bar (which is pinned to the stub shaft) deflects.
Since the spool valve is connected to the stub shaft by a
locating pin, torsion bar deflection causes the spool
valve to rotate within the valve body. As the spool valve
rotates, fluid directional passages in the valve are
brought into alignment with matching passages in the
valve body. When these passages are aligned, high pres
sure fluid from the pump is directed through the pas
sages and against either side of the rack piston to
provide hydraulic assist.
Torsion bar deflection provides the required amount
of steering gear "road feel." If the bar should ever break,
road feel would be lost but the steering system would
still function due to auxiliary locking tabs on the stub
shaft. In this situation, the gear would operate as a
manual-type recirculating ball steering gear.
Neutral (Straight-Ahead) Position
In this position, fluid does not enter the rack piston
chamber. Fluid from the pump flows through the open-
center valve body and back to the pump reservoir.
The valve body remains in the open center position at
all times, except when turning, to reduce fluid and pump
friction losses. In addition, the gear is always filled with
fluid to
shock.
POWER STEERING GEAR AND PUMP 2L-3
lubricate internal components and absorb road
Right Turn Position
The valve body is held in position by the resistance to
movement of the front wheels. When the steering wheel
is turned to the right, torsion bar deflection causes the
spool valve to rotate within the valve body.
As the spool valve rotates, the spool valve fluid return
grooves are closed off while the right turn grooves are
aligned with high pressure fluid grooves in the valve
body (fig. 2L-3). The spool valve left turn grooves are
closed off from pump pressure and are aligned with the
valve body fluid return grooves. In this position, the
valve body directs high presure fluid into the lower end
of the rack piston chamber to force the rack piston
upward and apply additional turning effort to the pit
man shaft (fig. 2L-3).
As the valve body directs fluid against the lower end
of the rack piston, fluid in the upper end of the gear
simultaneously flows back to the reservoir through
valve body return grooves. When front wheel resistance
to turning effort increases, torsion bar deflection causes
additional spool valve rotation. This exposes more of the
spool valve right turn grooves to the valve body pressure
grooves increasing fluid pressure exerted on the rack
piston.
When the driver stops applying turning effort at the
steering wheel, the torsion bar unwinds returning the
spool valve to the neutral (straight-ahead) position. At
this point, fluid pressure on each end of the rack piston
is equalized once again and steering geometry causes the
front wheels to resume a straight-ahead position.
Left Turn Position
In the left turn position, the torsion bar, spool valve,
and valve body operate the same as in a right turn
except that valve rotation is now reversed (fig. 2L-4).
This causes the valve body to channel high pressure
fluid into the upper end of the rack piston chamber
forcing the rack piston downward (fig. 2L-4). Fluid in
the lower end of the gear flows back to the pump reser
voir through the valve body and steering gear return
port.
When the driver stops applying turning effort at the
steering wheel, the torsion bar unwinds returning the
spool valve to the neutral (straight-ahead) position. As
in the right turn position, fluid pressure on each end of
the rack piston is equalized again and steering geometry
causes the front wheels to resume a straight-ahead
position.