Specifications

Vehicle System System Operation 30
The priority valve is integrated to the first block of
control valve. This section distributes oil to the
following areas based on, 1st brakes, 2nd steering,
and 3rd implement flow demand (mast/tilt/auxiliary
functions). The priority valve (2) supplies oil from
the pump (12) to brakes and steering unit (1) as
needed. The fluid is drawn from the hydraulic tank
(11) by the pump (12). The pump supplies fluid
through hydraulic hose (9) to a first block of control
valve (2).
When the steering unit (1) is neutral position, pilot
pressure in load sensing line (7) is reduced and the
spool of the priority valve is moved downward.
Most fluid goes passes through the neutral passage
of control valve and hydraulic line (10) back to
hydraulic tank (11)
When making a right turn, pilot pressure is
increased in load sensing line (7) forcing the priority
valve spool to moved toward the right. Oil flows
through hydraulic line (3) to the steering unit.
From the steering unit the oil flows through a
hydraulic line (5) filling the cylinder. This forces
the cylinder piston toward to opposite end of the
cylinder for a right turn. The piston movement
displaces oil from the opposite end of the cylinder
which returns to the steering unit though hydraulic
line (4) and hydraulic line (10) to the hydraulic tank
(11).
During a left turn, a pilot pressure is again
increased in load sensing line (7) which moves the
spool of priority valve upward. A fluid flows through
a hydraulic line (3) to a steering unit. From the
steering unit, the fluid flows through a hydraulic line
(4) to a power steering cylinder (6) to make a left
turn. The return fluid flows through a hydraulic line
(5) back to steering unit, a hydraulic line (8) and into
the hydraulic tank.
A check valve is installed into the port of steering
unit connected to hydraulic line(3) to prevent a fluid
back to priority valve right after a turn is made,
Relief valve in steering unit will open if steering
pressure goes above 9,000 (+300,-0) kPa or 1,305
(+43, -0) psi.
Steering Cylinder
Steering cylinder (1) gives power assistance through
the use of pressure oil at either end of the cylinder
piston.
The steering cylinder is double ended and the body of
the cylinder is mounted stationary to the steer axle.
The rod assembly is connected to the steering link
assembles at both ends of the cylinder which allows
the cylinder to move the link assemblies.
Steering Cylinder (Typical Example)
(1) Steering cylinder.
1