Bendix Commercial Vehicle Systems C-300N HYDRAULIC POWER STEERING1/99 - Manual (Page 6)

6
FIGURE 5 - SPINDLE ASSEMBLY WITH ROTARY VALVE COMPONENTS
FIGURE 8 - ROTARY VALVE OPERATION
BALL SCREW
(OUTER VALVE ELEMENT)
OIL IN
OIL OUT (RIGHT TURN)
OIL IN
SUPPLY
OIL OUT
LEFT TURN
TORSION BAR PIN
OIL RETURN (TO
PUMP RESERVOIR)
PIN HOLE
OIL OUT LEFT
TURN
OIL OUT RIGHT TURN
OIL OUT
RIGHT TURN
ROTARY VALVE
LONGITUDINAL
GROOVES (6)
(INSIDE HIDDEN
FROM VIEW)
OIL OUT
(LEFT TURN)
TORSION BAR
OIL IN
SUPPLY
OUTER VALVE
ELEMENT GROOVE
OIL RETURN (TO
PUMP RES.)
INNER VALVE
ELEMENT GROOVE
SPINDLE ASSEMBLY
TORSION
BAR PIN
OIL RETURN HOLES
(HIDDEN FROM VIEW)
INPUT SHAFT (INNER
VALVE ELEMENT)
TORSION BAR
STEERING
STOP
SPLINES
ROTARY
VALVE
GROOVES
(6)
OIL
RETURN
HOLE
(FROM
PISTON
CAVITY)
OIL RETURN
HOLES (TO
PUMP RES.)
INPUT SHAFT
(ROTARY VALVE
INNER ELEMENT)
INPUT SHAFT &
TORSION ASSEMBLY
BALL SCREW
(ROTARY VALVE
OUTER ELEMENT)
SPINDLE ASSEMBLY
OIL OUT
(LEFT TURN)
OIL IN
OIL OUT
RIGHT
TURN
INPUT SHAFT (INNER
VALVE ELEMENT) BALL SCREW
(OUTER VALVE
ELEMENT)
TO
PUMP
RES.
OIL IN
OIL OUT
RIGHT
TURN OIL OUT
(LEFT TURN)
OIL IN
OIL
RETURNING
FROM RIGHT
TURN SIDE OF
POWER
PISTON
OIL RETURNING
FROM LEFT TURN
SIDE OF POWER
PISTON
ROTARY CONTROL VALVE OPERATION
The rotary control valve is an open center type which allows
a continuous flow of oil (through the longitudinal grooves in
the input shaft and bore of the ball screw) when held in the
neutral position by the torsion bar.
When steering effort is applied, the input shaft and ball screw
tend to turn in unison, however the spring action of the torsion
bar results in the input shaft rotating slightly in advance of
the ball screw. The six pairs of grooves that form the rotary
control valve are displaced from their neutral flow position.
As steering effort increases, so does the amount of
displacement. Depending on the direction steered, the groove
displacement of the input shaft directs hydraulic oil through
the appropriate drilled passages in the ball screw to one
side or the other of the piston. Hydraulic pressure acting
TO
PUMP
RES.
TO
PUMP
RES.
LEFT TURN
NEUTRAL RIGHT TURN