Advance acoustic 56514925, Service Manual

Page: 217 / 260

Steering System 217 Service Manual – Advance 7765 / Nilfisk CR1500
Hydraulic Diagrams
Power Steering Unit Description
The
Power Steering Unit
uses the
input from the steering wheel to turn
the drive wheel in the appropriate
direction to steer the machine. When
the Operator turns the steering wheel,
the steering wheel shaft rotates the
rotary
Valve
spool and
Gerotor Metering
Mechanism
, which are connected by
the
Direct Mechanical Link
inside of the
Power Steering Unit
.
• The direction in which the
Valve
moves determines which side of
the
Power Steering Cylinder
receives
the hydraulic oil to turn the drive
wheel left or right. Note that when
the Operator stops turning the
steering wheel, the springs in the
Power Steering Unit
return the
Valve
to the neutral (closed) position to
hold the
Power Steering Cylinder
rod
in its current position.
• The number of degrees that the
Gerotor Metering Mechanism
rotates
determines the volume of oil that
the
Power Steering Cylinder
receives
from the
Valve
. This allows the
drive wheel to turn in proportion to
the steering wheel rotation.
Steering Wheel Stationary
When the engine is running, the
Auxiliary Pump
sends oil through the
priority flow divider to the “
P
” port
on the
Power Steering Unit
. When the
steering wheel is stationary, the
Valve
is in its neutral (closed) position.
The hydraulic oil flows through the
U-shaped ports in the
Valve
, through
the “
T
” port on the
Power Steering
Unit
, then to the
Cylinder Control Valve
.
Note that when the steering wheel is
stationary, the
Valve
ports are blocked
and the
Power Steering Cylinder
will
maintain its current position.
Power
Steering
Unit
1500
PSI
3.05
CIR
P T
Power Steering
Cylinder
L R
Steering
Centered
Reservoir
Auxiliary
Pump
1.02
CIR
1.5 GPM
To Cylinder
Control Valve
To Squeegee
Vacuum Motor
Gerotor
Metering
Mechanism
Valve
Direct
Mechanical
Link