Design and Operation
Operating pressure
Return line pressure
Reduced
operating pressure
Return line pressure
6 Instructions on Design, Operation, Maintenance and Inspection
3 Operation of the hydraulic steering limitation
The hydraulic steering limitation prevents a steering to the lock stops at full hydraulic pressure.
I
t, thus, protects the pump and the steering linkage and prevents high oil temperatures.
A double-acting steering limiting valve with spring-loaded valve pins (T and U) is arranged in the
longitudinal direction in the piston (B). The valve pins project over the right-hand and the left-hand
front faces of the piston (Fig. 4).
Fig. 4 Steering limiting valve
closed
T Right-hand valve pin of
steering limiting valve
U Left-hand valve pin of
steering limiting valve
V Right-hand cylinder chamber
W Left-hand cylinder chamber
X Right-hand adjusting screw
Y Left-hand adjusting screw
If the piston is shifted to the right or to the left towards the lock stop, the valve pins (T and U)
are actuated by the adjusting screws (X and Y) fastened in the housing and the cylinder cover,
respectively. The steering limiting valve remains closed until one of the valve pins hits against an
adjusting screw.
If for instance the piston is displaced to the right (Fig. 5), the right-hand valve pin will hit against
the adjusting screw (X) before the piston end position is reached. Valve pin (U) is displaced by
the oil pressure so that the oil can flow away from cylinder chamber (W) to cylinder chamber (V)
and from there to the return line. When the piston is displaced to the left, the same sequence of
operations as described above will take place by analogy.
Fig. 5 Piston displacement to the right. Right-hand valve pin open. Oil pressure greatly reduced.
As soon as the steering limiting valve is open, the steering gear can be turned forward further at
an increased steering effort and with greatly reduced hydraulic assistance until the lock stop is
reached.
To Next Page
Loading...