Claas K5D00100, Repair Manual

Page: 56 / 252

AXLES & STEERING 1.46
Steering
Description
The steering system is fully hydrostatic. This means
that the steering motion is transmitted hydraulically
with no mechanical linkage between the steering
wheel and the steered wheels. The hydraulic supply
is by a dynamic system working with a load-sensing
(LS) pump. Pump supply passes through a priority
valve and generates a load-sensing signal.
Operation
The OSPF steering unit interfaces the steering valve
with an adapter. Depending on the steering mode
selected in the cab, (two-wheel steer, four-wheel
steer or crab steer), the selector valve directs oil to
the selected steering cylinder when input is made
from the steering wheel.
In the neutral position, oil is allowed to flow freely
from the priority valve through the steering unit to
return (LS to T). As the steering wheel is turned the
spools of the valve rotate against each other and
proportionally direct oil to the selected steering
cylinder. Not until the rotary valve is fully open is the
LS connection to the tank fully closed.
A pressure relief valve is fitted in the steering unit. If
the pressure rises above 175 bar (2537 psi), the
PRV will open and return excess pressure to tank.
Shock valves are fitted to in the steering unit to
protect the cylinders and hoses and are set at a
higher pressure than the PRV.
When hydraulic pressure fails, the vehicle can be
steered manually. The steering wheel, when turned,
drives the outer spool with the cross pin and the
rotor is turned by the cardan shaft which acts as a
manual pump to supply oil to the steering cylinder.
In this case the steering effort required will be
increased significantly.
Specification
Type OSPF250LS
PRV 170-175 bar (2465-2537 psi)
Shock valve 225-245 bar (3262-3552 psi)
Displacement 250 cu.cm/rev
C3 To front cylinder
O OSPF250 valve (21)
A Adapter
E Selector valve (22)
C1 To rear cylinder
C2 To rear cylinder
C4 To front cylinder
P Pressure from LS – pump
T Tank