Pressure/Flow Regulator Valve - jcb 214e Service Manual

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Section E Hydraulics Section E
5 - 5 Circuit Descriptions 5 - 5
Hydraulic Pump - Variable Flow

Pressure/Flow Regulator Valve

The pressure and flow regulator valve assembly is mounted
5
to the pump. The valve maintains the pump pressure and
flow rate in accordance with demand at the service valve
blocks.
4
Load Sensing - Stand-by Position
Stand-by is when the machine is running but the control
levers are in neutral position, i.e. no implements are being
3
used. There is no pressure or flow demands on the pump,
therefore there will be no pressure signal .
P A T
With the engine switched off, spring 1 holds swashplate 2 at
the maximum angle. When the engine is started and the
pump begins to turn, oil begins to flow and pressure builds in
7
the closed centre hydraulic system.
2
Valve 5 houses a flow regulator spool 4 and pressure
regulator spool 3. Pressure which is building in the closed
centre system is sensed at port P of the regulator valve. The
increasing pressure pushes flow compensating spool 4 up
against its spring 6. This movement creates a flow path from
port P to port A. Oil now flows from the flow regulator valve
(via port A) to swashplate control piston 7.
The control piston now moves the swashplate 2 towards its
1
minimum angle. As the piston moves towards its full travel
position, cross-drilled holes 8 are uncovered allowing oil to
drain.
A275760
The cross-drilled holes limit the travel of the control piston -
when the holes are exposed, pump flow is insufficient to
make up for leakage through the holes and maintain the
pressure behind the control piston. Therefore the piston
m o ves b ac k t o p art ially c o ver t he c ro ss ho les t hus
maintaining enough flow to cater for normal system leakage
w hilst est ab lishing a syst em st and - b y p ressure (see
Technical Data for pressure).
9803/3280 Issue 1
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