SHOP MANUAL
HYDRAULIC
Ch 5 page 36 Ch 5 page 37
HYDRAULIC
Steering system
Description:
The steering system is built up of an orbitrol steering unit, a steering valve dinamic flow amplifier and two steer-
ing cylinders.
When the orbitrol is activated, a controlled oil flow is directed to the flow amplifier.
This oil flow is amplified in the flow amplifier and the total oil flow is directed to the steering cylinders.
The orbitrol has a displacement of 160cm3/rev
(DA30)
and 250cm3/rev
(DA40)
and the amplification factor is 8.
This means that total displacement is 160 cm3 x 8 = 1280 cm3(DA30) and 250 cm3 x 8 = 2000(DA40) per
steering wheel revolution.
In the flow amplifier system, it is a combination between steering and working hydraulics.
A priority valve is built into the flow amplifier. The priority valve ensures that the steering system has first priority
on oil flow from the hydraulic pumps, which enters the flow amplifier.
The oil flow which is not used for steering, are sent to tank.
If the steering wheel is not turned, the entire oil flow is directed to the tipping valve.
The principle applied to the controlled operation of the flow amplifier, called “load sensing”. As name suggest ,
it is a system in which the load is used in this system, to control the priority valve in the flow amplifier, so that
oil flow and pressure precisely matches momentary demands.
Figure 18
P
T
HT
L
R
TANK
To HP Port
From LS Port
X
S (In)
P (Out)
T
L
P R
LS
RHS LHS
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