Eaton Compressor & Fabrication C-STOV-MC001-E1 User Manual

Page 6

EATON Char-Lynn Steering Catalog C-STOV-MC001-E1 July 2006

Hydraulic Circuit
Explanation

Neutral Circuits:
Open Center
and Open Center
Power Beyond

Fixed
Displacement
Pump

Gerotor

PB P

Fixed
Displacement
Pump

To Auxilliary Circuit
Open Center Valves

Open Center

• Simplest, most

economical system

• Uses a fixed

displacement pump

• In neutral position

pump and tank are
connected

• Most suitable on

smaller type vehicles

Open Center Power Beyond

The power beyond steering
control unit supplies steering
and auxiliary valve functions.
The power beyond unit is
used on medium pressure,
open center (fixed
displacement pump) systems.

When not steering, the power
beyond unit directs all inlet
flow to the auxiliary circuit.
However once steering is
initiated, part of the auxiliary
flow is diverted to steering.
Since steering has priority, all
flow, if required, will be
diverted to steering. The tank
port of the steering unit has
flow only when steering is
operated. Thus, flow out of
the auxiliary (“PB”) port and
the tank port will fluctuate or
stop depending on steering
input.

The following special
considerations should be
addressed when applying
power beyond steering:

• Auxiliary valves

(connected to PB) must
be open center type.
Slight bump or kick may
be felt in steering
wheel when auxiliary
functions are activated
during steering
operations.

• Pump flow not used for

steering is available at
power beyond (PB)
outlet, except at
steering stops where
total pump flow goes
over the system relief
valve. Avoid auxiliary
functions that require
constant flow while
steering.

• Flow is only directed to

the tank port when
steering is operated.
Avoid systems where
return flow from tank
port is used for auxiliary
functions.

• Inlet pressure to the

steering unit will be the
higher of steering
system pressure or
auxiliary valve pressure.

• Generally avoid

systems where heavy
use of auxiliary
functions occur while
steering.

Applications

• Lawn and Garden

Equipment

• Utility Vehicles