3
HGF Series Service Procedure
Satisfactory performance of the overall hydraulic system
requires a well-engineered installation. The hydraulics
must meet the design features of the vehicle and
contribute to the operation for which the vehicle was built.
Make no changes to the steering system without first
consulting qualified factory service personnel. Ross
Gear extends engineering advice and welcomes
requests for assistance.
Engineering contacts can provide information on such
hydraulic components as pumps, cylinders, and fluid
lines. The HGF control unit works best with a balanced-
area cylinder design.
HGF: Design
The HGF Hydraguide unit consists of a fluid control valve
section and a fluid metering section. These are
hydraulically and mechanically interconnected inside the
unit.
Control Valve Section: Operation
The HGF Hydraguide uses a servo-reactive (feedback
control) valve which is centered by two sets of three coil
springs. The valve regulates pressure and directs pump
flow to the steering cylinder or cylinders. The valve is of
the open-center type: when in the neutral position, it
allows fluid to flow from the pump to the pressure port,
through the HGF unit to the return port, and back to the
reservoir.
The valve is available in open- or closed-cylinder
configurations, each of which brings its own advantages
to bear in the hydraulic system.
Open Cylinder: cylinder ports are open to the metering
pump, allowing road or ground reaction to rotate and
recenter the valve, as the vehicle's steering geometry
provides recentering forces. When the driver completes
a turn, the steering will recenter, as happens, for
example, in most automobile power steering systems.
Closed Cylinder: cylinder ports are blocked to the
metering pump, preventing road or ground reaction from
rotating and recentering the valve. The driver must steer
to "straight ahead" or another position. This design is
useful in a vehicle which must remain turned while the
driver takes his hands off the steering wheel to operate
other controls.
Metering Section: Operation
The metering section performs three functions:
• It meters (measures) fluid to the cylinder or cylinders:
• It maintains the ratio of hand wheel turns to the
direction of the steered wheels; and
• It acts as a pump for manual steering in the event high-
pressure fluid does not reach the HGF unit.
HGF: Design and Operation
(See HGF Design Features and Design Illustration)
Содержание Hydraguide HGF Series
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