SECTION 9
STEERING
configuration opposite the cavity. Due to the interaction
(3) a metering section.
between the rotor and stator, there are 42 overlapping fluid
discharging actions in one revolution of the rotor.
The column section provides a means of mounting and
actuating the control and metering sections. The control
section distributes the oil to and from the metering section.
9-15.
OPERATION (see figure 9-2).
The metering section determines the quantity of oil
delivered to the control section.
9-16. Rotation of the steering wheel actuates three main
components in the steering control unit:
9-10. The column section consists of a splined shaft and
(1) The control section spool
housing assembly. The unit steering wheel is splined to
one end of the shaft. The opposite end of the shaft is
(2) The control section sleeve
splined into the control section spool to rotate the spool for
distribution of oil.
(3) The metering element (rotor) in the metering
section.
9-11. The control section consists of a spool and sleeve
assembly, six centering springs and a manual steering
When the steering wheel is stationary, the control section
check valve mounted in a cast housing. The housing also
spool and sleeve are held in the center position by the six
contains an inlet port, a dump port and two steering
centering springs. During this condition, oil is received
cylinder ports. The spool is fitted into the center of the
from the system hydraulic pump and is routed back to the
sleeve and is held in place in the sleeve by a straight pin
tank.
and the set of six centering springs. The pin extends
through the sleeve and two radial slots in the spool. The
9-17. As the steering wheel is turned and the spool just
pin is a tight fit in the sleeve and a loose fit in the spool.
begins to rotate, the spring set tends to rotate the sleeve to
The centering springs extend through the spool and out
maintain the "center" relationship between the spool and
each side of the sleeve so that they return the spool to the
sleeve. However, the force required to turn the rotor set is
center position. The spool contains a series of porting
greater than the spring pressure and the6springs start to
holes that align with similar holes in the sleeve when the
flex. This "flexing" action permits the spool to move within
spool is rotated off of the center position.
the sleeve (approximately 1/8 inch) until the ends of the
spool slots contact the straight pin extending through the
9-12. A shaft with a radial slot at one end and splines at
sleeve and the spool. In this position, the porting holes in
the opposite end connects the control section to the
the sleeve and spool are aligned. This permits incoming
metering section. The slotted end of the shaft mates with
oil to flow to the metering section and opens one of the
the straight pin extending through the spool. The splined
cylinder ports.
end fits into the center of the rotor set closest to the control
section. The control section is also attached to the
9-18. Further rotation of the steering wheel causes the
metering section through a porting plate.
spool to rotate the pin, which then turns the sleeve and the
rotor in the metering section. At this time, oil is being
9-13. The metering section consists of a rotor set
metered by the metering section and is allowed to flow
(metering element) which is connected to the control
through the spool and sleeve to one side of the steering
section spool. The rotor set consists of a matched rotor
cylinder. The porting arrangement also allows the oil to
and stator.
flow from the opposite side of the cylinder, through the
control section and back to the hydraulic tank. The output
9-14. The stator has seven concave configurations
of the metering section is directly proportional to the speed
(serving as oil cavities). It also contains the same number
and distance that the steering wheel rotates.
of convex configurations, each one being diametrically
opposite a cavity. The rotor contains six lobes that are
9-19. When rotation of the steering wheel stops, the
formed to mate with the stator cavities. Each lobe has a
metering action in the metering section also stops. The six
diametrically opposite lobe: therefore when one rotor is in a
centering springs then return the sleeve to the neutral
cavity of the stator, its opposite lobe is at the crest of the
(open-center) position. When this occurs,
stator convex
9-3.
