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Section E
Hydraulics
Section E
5 - 7
Circuit Descriptions
5 - 7
Hydraulic Pump - Variable Flow
Pressure/Flow Regulator Valve
Load Sensing - Maximum Flow
5
When a service is operated, the signal pressure from the
loader (or backhoe) valve 13 increases. The increase in signal
6
pressure combined with the force of spring 6 moves spool 4
4
down. Oil in control piston 7 is allowed to drain back to the
tank via restrictor 9 and passage 10.
The force of spring 1 is now sufficient to increase the angle
3
of swashplate 2. The increased angle of the swashplate
increase the output of the pump.
P
A
T
The p ump out p ut p ressure w ill c ont inue t o inc rease,
eventually the pressure will move flow regulating spool 4
against the force of spring 6 and the signal pressure in cavity
7
11. Pump output pressure is now sent to control piston 7 via
port A. Control piston 7 will overcome the force of spring 1.
2
The pump swashplate angle decreases and therefore the
pump outlet decreases. Eventually the pressure in the load
sense line and the force of spring 6 will move spool 4 down
and the 'metering' cycle starts again.
The up and down movement of the spool 4 keeps the
pressure on both ends of the spool equal. Spring 6 is
2
eq uivalent t o 20 b ar (290 lb f/ in
), t herefore t he p ump
pressure should be this amount greater than the signal
1
pressure (except when at maximum pressure - see Load
Sensing - Maximum Pressure (no flow).
A275770
9803/3280
Issue 1
Purchased from www.WorkshopManuals.co.uk
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