10-18
3.2 LOAD SENSING (LS) VALVE
FUNCTION
·
The
LS
valve controls the pump delivery according to the stroke of the directional control valve lever, i.e., according
to the demand for oil flow from the actuators.
·
The
LS
valve determines the demand from the actuators by way of the pressure difference
D
PLS
between the pump
delivery pressure
PP
and the pressure
PLS
at the outlet of the directional control valve; this difference is then used to
control the delivery
Q
of the hydraulic pump.
(
PP
,
PLS
and
D
PLS
, are respectively: the pump delivery pressure, the pressure of the Load Sensing signal and the
pressure difference between these two values).
·
In other terms, the
LS
valve determines the pressure difference
D
PLS
, generated by the flow of oil through the pas-
sage opened up by the directional control valve spool and controls the pump delivery
Q
so as to maintain a constant
pressure difference.
The pump delivery can thus be said to be proportional to the demand from the directional control valve.
OPERATION
The operation of the pump can be described in four main stages:
a. When the directional control valve is in neutral position
b. When a control valve lever is operated
c. When the delivery stabilizes
d. When the system enters a state of “saturation”
LOAD SENSING VALVE, PRESSURE CONTROL VALVE
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